Anisotropic electrically conductive film, method for producing same, and connection structural body

ABSTRACT

The present invention provides an anisotropic electrically conductive film with a structure, in which electrically conductive particles are disposed at lattice points of a planar lattice pattern in an electrically insulating adhesive base layer. A proportion of the lattice points, at which no electrically conductive particle is disposed, with respect to all the lattice points of the planar lattice pattern assumed as a reference region, is less than 20%. A proportion of the lattice points, at which plural electrically conductive particles are disposed in an aggregated state, with respect to all the lattice points of the planar lattice pattern, is not greater than 15%. A sum of omission of the electrically conductive particle and an aggregation of the electrically conductive particles is less than 25%.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.16/382,684 filed Apr. 12, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/522,162 filed Apr. 26, 2017, which is a NationalStage of International Application No. PCT/JP2015/080337 filed Oct. 28,2015, which claims priority of Japanese Patent Application No.2014-219792 filed Oct. 28, 2014, Japanese Patent Application No.2014-219791 filed Oct. 28, 2014, Japanese Patent Application No.2014-219790 filed Oct. 28, 2014, and Japanese Patent Application No.2014-219789 filed Oct. 28, 2014. The entire contents of each of theabove mentioned documents are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an anisotropic electrically conductivefilm.

BACKGROUND ART

An anisotropic electrically conductive film, in which electricallyconductive particles are dispersed in an electrically insulating resinbinder, is widely used when an electronic component such as an IC chipis mounted on a wiring board and the like; however, in such ananisotropic electrically conductive film, it is known that electricallyconductive particles are present in a state of being connected oraggregated with one another. Therefore, in a case where the anisotropicelectrically conductive film is applied to connect IC chip terminals andwiring board terminals, the pitches of which are reduced as anelectronic device is reduced in a weight thereof and miniaturized, ashort circuit may occur between the adjacent terminals due to theelectrically conductive particles that are present in a state of beingconnected or aggregated in the anisotropic electrically conductive film.

Conventionally, a film, in which electrically conductive particles areregularly arranged, is suggested as an anisotropic electricallyconductive film to deal with such a narrow pitch. For example, ananisotropic electrically conductive film is suggested which is obtainedas follows: after an adhesive layer is formed in a stretchable film andthe electrically conductive particles are densely packed in a singlelayer on a surface of the adhesive layer, the film is biaxiallystretched until the distance between the conductive particles reaches apredetermined distance to arrange the electrically conductive particlesregularly, then the electrically conductive particles are transferred toan electrically insulating adhesive base layer by pressing anelectrically insulating adhesive base layer against the electricallyconductive particles, the electrically insulating adhesive base layerbeing an element of the anisotropic electrically conductive film (PatentDocument 1). Alternatively, an anisotropic electrically conductive filmis also suggested which is obtained as follows: electrically conductiveparticles are scattered on a transfer-type concave portion formationsurface having a concave portion on a surface, the concave portionformation surface is squeegeed and the electrically conductive particlesare held in the concave portion, the electrically conductive particlesare primarily transferred to the adhesive layer by pressing therefrom anadhesive film on which an adhesive layer for transfer is formed. Next,the electrically conductive particles deposited on the adhesive layerare transferred to an electrically insulating adhesive base layer bypressing the electrically insulating adhesive base layer against theelectrically conductive particles being deposited to the adhesive layer,the electrically insulating adhesive base layer being an element of theanisotropic electrically conductive film (Patent Document 2). Ingeneral, in these anisotropic electrically conductive films, anelectrically insulating adhesive cover layer is laminated on the surfaceof the electrically conductive particle side to cover the electricallyconductive particles.

CITATION LIST Patent Literature

Patent Document 1: WO 2005/054388

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 2010-033793A

SUMMARY OF INVENTION Technical Problem

However, the electrically conductive particles are easily aggregated toform secondary particles by static electricity and the like, and thus,it is difficult for the electrically conductive particles to be presentisolated all the time as primary particles. Therefore, the followingproblems arise in the technologies of Patent Documents 1 and 2. That is,in the case of Patent Document 1, there was a problem that it isdifficult to densely pack the electrically conductive particles on theentire surface of a stretchable film in a single layer with no defects,thus, the electrically conductive particles may be packed in thestretchable film in an aggregated state, resulting in a cause of a shortcircuit; or a region, in which no electrically conductive particle ispacked (so-called “omission of an electrically conductive particle”) maybe created, resulting in a cause of a conduction failure. In the case ofPatent Document 2, the following problems may occur: if thetransfer-type concave portion is covered with electrically conductiveparticles having a large particle diameter, the electrically conductiveparticles are removed by a subsequent squeegee, a concave portion thatdoes not hold the electrically conductive particles may be created, and“omission of an electrically conductive particle” may occur in theanisotropic electrically conductive film causing a conduction failure;or, conversely, if a large number of small electrically conductiveparticles are pressed in the concave portion and transferred to theelectrically insulating adhesive base layer, an aggregation of theelectrically conductive particles may occur, and further, theelectrically conductive particles located on the base side of theconcave portion may not be in contact with the electrically insulatingadhesive base layer, and thus the electrically conductive particles maybe dispersed on the surface of the electrically insulating adhesive baselayer, resulting in a loss of a regular arrangement, causing a shortcircuit and a conduction failure.

As seen above, in Patent Documents 1 and 2, in reality, a sufficientconsideration is not given to the way how to control the “omission” and“aggregation” of the electrically conductive particles that should bedisposed with a regular pattern on the anisotropic electricallyconductive film.

An object of the present invention is to solve the above-describedconventional technical problems, and from a viewpoint of “omission” and“aggregation” of the electrically conductive particles that should bedisposed with a regular pattern, to provide an anisotropic electricallyconductive film in which occurrence of a short circuit or a conductionfailure is significantly suppressed.

Solution to Problem

The present inventor discovered that it is possible to achieve theabove-described object by controlling, when disposing electricallyconductive particles at lattice points of a planar lattice, with respectto all the lattice points of the planar lattice pattern assumed as areference region of an anisotropic electrically conductive film, a“proportion of the lattice points at which no electrically conductiveparticle is disposed”, a “proportion of the lattice points at whichplural electrically conductive particles are disposed in an aggregatedstate”, and an “aggregation direction of the aggregated electricallyconductive particles” where necessary. Furthermore, the presentinventors discovered that it is also possible to achieve theabove-described object when, with respect to all the lattice points ofthe planar lattice pattern assumed as a reference region of ananisotropic electrically conductive film, a “proportion of the latticepoints at which no electrically conductive particles is disposed” and a“proportion of the lattice points at which plural electricallyconductive particles are disposed in an aggregated state” are controlledand in addition, when at least some of the aggregated electricallyconductive particles are disposed with a shift in a thickness directionof the anisotropic electrically conductive film. Then, the presentinvention was completed on the basis of the acquired knowledge.Furthermore, the present inventors also discovered that it is possibleto produce such an anisotropic electrically conductive film, not bydisposing the electrically conductive particles in a concave portion ofa transfer body, but by depositing the electrically conductive particleson a tip end of a columnar convex portion of the transfer body of whichthe surface is formed with the convex portion, followed by transfer.Thus, the present inventors completed a production method of the presentinvention.

That is, according to an embodiment of the present invention, ananisotropic electrically conductive film having a structure is provided,in which electrically conductive particles are disposed at latticepoints of a planar lattice pattern in an electrically insulatingadhesive base layer, wherein a proportion of the lattice points, atwhich no electrically conductive particle is disposed, with respect toall the lattice points of the planar lattice pattern assumed as areference region of the anisotropic electrically conductive film (aproportion of the lattice points with “omission of an electricallyconductive particle”) is less than 20%, a proportion of the latticepoints, at which plural electrically conductive particles are disposedin an aggregated state, with respect to all the lattice points of theplanar lattice pattern (a proportion of the lattice points with“aggregation” of electrically conductive particles) is 15% or less, anda sum of the omission and the aggregation is 25% or less.

More specifically, the anisotropic electrically conductive film of thepresent invention provides an anisotropic electrically conductive filmof first to fourth modes below.

That is, the present invention provides, as a first mode, an anisotropicelectrically conductive film with a structure, in which an electricallyinsulating adhesive base layer and an electrically insulating adhesivecover layer are laminated together, and near an interface therebetween,electrically conductive particles are disposed at lattice points of aplanar lattice pattern, wherein a proportion of the lattice points, atwhich no electrically conductive particle is disposed, with respect toall the lattice points of the planar lattice pattern assumed as areference region of the anisotropic electrically conductive film is lessthan 20%, and a proportion of the lattice points, at which pluralelectrically conductive particles are disposed in an aggregated state,with respect to all the lattice points of the planar lattice pattern is5% or less. In the first mode, it is preferable that a sum of theomission and the aggregation is less than 25%.

Furthermore, the present invention provides, as a second mode, ananisotropic electrically conductive film having a structure in which anelectrically insulating adhesive base layer and an electricallyinsulating adhesive cover layer are laminated together, and near aninterface therebetween, electrically conductive particles are disposedat lattice points of a planar lattice pattern, wherein a proportion ofthe lattice points, at which no electrically conductive particle isdisposed, with respect to all the lattice points of the planar latticepattern assumed as a reference region of the anisotropic electricallyconductive film is less than 5%, and a proportion of the lattice points,at which plural electrically conductive particles are disposed in anaggregated state, with respect to all the lattice points of the planarlattice pattern is greater than 10% and less than 15%. In the secondmode, it is preferable that a sum of the omission and the aggregation isless than 20%.

The present invention provides, as a third mode, an anisotropicelectrically conductive film having a structure, in which anelectrically insulating adhesive base layer and an electricallyinsulating adhesive cover layer are laminated together, and near aninterface therebetween, electrically conductive particles are disposedat the lattice points of the planar lattice pattern, wherein aproportion of the lattice points, at which no electrically conductiveparticle is disposed, with respect to all the lattice points of theplanar lattice pattern assumed as a reference region of the anisotropicelectrically conductive film, is 15% or less, a proportion of thelattice points, at which plural electrically conductive particles aredisposed in an aggregated state, with respect to all the lattice pointsof the planar lattice pattern, is 10% or less, and the electricallyconductive particles disposed in an aggregated state are aggregated in aplanar direction of the anisotropic electrically conductive film. In thethird mode, it is preferable that a sum of the omission and theaggregation is 25% or less.

That is, the present invention provides, as a fourth mode, ananisotropic electrically conductive film having a structure, in which anelectrically insulating adhesive base layer and an electricallyinsulating adhesive cover layer are laminated together, and near aninterface therebetween, electrically conductive particles are disposedat the lattice points of the planar lattice pattern, wherein aproportion of the lattice points, at which no electrically conductiveparticle is disposed, with respect to all the lattice points of theplanar lattice pattern assumed as a reference region of the anisotropicelectrically conductive film, is less than 10%, a proportion of thelattice points, at which plural electrically conductive particles aredisposed in an aggregated state, with respect to all the lattice pointsof the planar lattice pattern, is 15% or less, and at least some ofelectrically conductive particles that are disposed in an aggregatedstate are disposed with an oblique shift in a thickness direction of theanisotropic electrically conductive film. In the fourth mode, it ispreferable that a sum of the omission and the aggregation is less than25%.

The present invention provides a method of producing the above-mentionedanisotropic electrically conductive film having a structure, in which anelectrically insulating adhesive base layer and an electrically adhesivecover layer are laminated together, and near an interface therebetween,electrically conductive particles are disposed at the lattice points ofthe planar lattice pattern, specifically, the anisotropic electricallyconductive film of the first, second, third, or fourth mode, including:

(i) preparing a transfer body having a columnar convex portioncorresponding to a lattice points of a planar lattice pattern, formed ona surface thereof;

(ii) making at least a top surface of the convex portion of the transferbody as a weak adhesive layer;

(iii) depositing electrically conductive particles on the weak adhesivelayer of the convex portion of the transfer body;

(iv) transferring the electrically conductive particles to anelectrically insulating adhesive base layer by overlapping and pressingthe electrically insulating adhesive base layer on a surface at a sideof the transfer body on which the electrically conductive particles aredeposited; and

(v) laminating an electrically insulating adhesive cover layer to theelectrically insulating adhesive base layer, on which the electricallyconductive particles are transferred, from a side, on which theelectrically conductive particles are transferred.

Furthermore, according to an embodiment of the present invention, aconnection structural body, in which a terminal of a first electroniccomponent and a terminal of a second electronic component areanisotropically conductively connected by the above-describedanisotropic electrically conductive film, specifically, the anisotropicelectrically conductive film of the first, second, third, and fourthmodes.

Advantageous Effects of Invention

In the anisotropic electrically conductive film of the presentinvention, a proportion of “lattice points, at which no electricallyconductive particle is disposed” (proportion of the lattice points atwhich an electrically conductive particle is not present) with respectto all the lattice points of the planar lattice pattern assumed as areference region is set to less than 20%, and a proportion of “latticepoints at which plural electrically conductive particles are disposed inan aggregated state” (proportion of the lattice points at which theelectrically conductive particles are aggregated) is 15% or less, andmoreover, a sum of the omission and the aggregation is set to 25% orless. Therefore, when the anisotropic electrically conductive film ofthe present invention is applied to an anisotropic conductiveconnection, it is possible to achieve a good initial conductivity and agood conduction reliability after aging, and it is also possible tosuppress occurrence of a short circuit. Furthermore, in addition to COG,it is excellent for electronic components having a relatively large bumparea and a distance between the bumps such as FOG in terms of economy.

In a method of producing an anisotropic electrically conductive filmaccording to an embodiment of the present invention, a transfer body, inwhich a columnar convex portion corresponding to lattice points of aplanar lattice pattern is formed on a surface is used, electricallyconductive particles are deposited on a weak adhesive layer formed on atop surface of the convex portion, and then the electrically conductiveparticles are transferred to an electrically insulating adhesive baselayer. Therefore, it is possible to achieve that a proportion of“lattice points, at which no electrically conductive particle isdisposed” with respect to all the lattice points of the planar latticepattern assumed as the reference region of the anisotropic electricallyconductive film is less than 20%, and a proportion of “lattice points,at which plural electrically conductive particles are disposed in anaggregated state” with respect to all the lattice points of the planarlattice pattern is 15% or less. Thus, by using the method of productionof the present invention, it is possible to economically advantageouslyproduce an anisotropic electrically conductive film, and with theanisotropic electrically conductive film, it is possible to achieve ananisotropic conductive connection between an IC chip and a wiring board,wherein the pitches are reduced while occurrence of a short circuit anda conduction failure are significantly suppressed.

In the anisotropic electrically conductive film of the first mode of thepresent invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as a referenceregion is set to less than 20%, and moreover, a proportion of “latticepoints at which plural electrically conductive particles are disposed inan aggregated state” with respect thereto is 5% or less. Therefore, whenthe anisotropic electrically conductive film of the present invention isapplied to an anisotropic conductive connection, it is possible toachieve a good initial conductivity and a good conduction reliabilityafter aging, and it is also possible to suppress occurrence of a shortcircuit. Furthermore, in addition to COG, it is excellent for electroniccomponents having a relatively large bump area and a distance betweenthe bumps such as FOG in terms of economy.

In a method of producing an anisotropic electrically conductive film ofthe first mode of the present invention, by using a transfer body havinga columnar convex portion corresponding to a lattice point region of aplanar lattice pattern, formed on a surface thereof, electricallyconductive particles are deposited on a weak adhesive layer formed on atop surface of the convex portion, then the electrically conductiveparticles are transferred to an electrically insulating adhesive baselayer. Therefore, it is possible to achieve that a proportion of“lattice points, at which no electrically conductive particle isdisposed” with respect to all the lattice points of the planar latticepattern assumed as the reference region of the anisotropic electricallyconductive film is less than 20%, and a proportion of “lattice points,at which plural electrically conductive particles are disposed in anaggregated state” with respect to all the lattice points of the planarlattice pattern is 5% or less. Thus, by using the method of productionof the present invention, it is possible to economically advantageouslyproduce an anisotropic electrically conductive film, and with theanisotropic electrically conductive film, it is possible to achieve ananisotropic conductive connection between an IC chip and a wiring board,wherein the pitches are reduced while occurrence of a short circuit anda conduction failure are significantly suppressed.

In the anisotropic electrically conductive film of the second mode ofthe present invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as the referenceregion is set to less than 5%, and moreover, a proportion of “latticepoints at which plural electrically conductive particles are disposed inan aggregated state” is set to greater than 10% and less than 15%.Therefore, when the anisotropic electrically conductive film of thepresent invention is applied to an anisotropic conductive connection, itis possible to achieve a good initial conductivity and a good conductionreliability after aging, and it is also possible to suppress occurrenceof a short circuit. Furthermore, in addition to COQ it is excellent forelectronic components having a relatively large bump area and a distancebetween the bumps such as FOG in terms of economy.

In a method of producing an anisotropic electrically conductive film ofthe second mode of the present invention, by using a transfer bodyhaving a columnar convex portion corresponding to a lattice point regionof a planar lattice pattern, formed on a surface thereof, electricallyconductive particles are deposited on a weak adhesive layer formed on atop surface of the convex portion, then the electrically conductiveparticles are transferred to an electrically insulating adhesive baselayer. Therefore, it is possible to achieve that a proportion of“lattice points, at which no electrically conductive particle isdisposed” with respect to all the lattice points of the planar latticepattern assumed as any reference region of the anisotropic electricallyconductive film is less than 5%, and a proportion of “lattice points, atwhich plural electrically conductive particles are disposed in anaggregated state” with respect to all the lattice points of the planarlattice pattern is greater than 10% and less than 15%. Consequently, inthe production method according to an embodiment of the presentinvention, it is possible to economically advantageously produce ananisotropic electrically conductive film, and by using the anisotropicelectrically conductive film, it is possible to anisotropic conductiveconnect between the IC chip and the wiring board, wherein the pitchesthereof are reduced while occurrence of a short circuit and a conductionfailure are significantly suppressed.

In the anisotropic electrically conductive film of the third mode of thepresent invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as the referenceregion is set to 15% or less, moreover, a proportion of “lattice points,at which plural electrically conductive particles are disposed in anaggregated state” is set to 10% or less, and moreover, the electricallyconductive particles disposed in an aggregated state are aggregated in aplanar direction of the anisotropic electrically conductive film.Therefore, when the anisotropic electrically conductive film accordingto an embodiment of the present invention is applied to an anisotropicconductive connection, it is possible to achieve a good initialconductivity and a good conduction reliability after aging, and it isalso possible to suppress occurrence of a short circuit. Furthermore, inaddition to COG, it is excellent for electronic components having arelatively large bump area and a distance between the bumps such as FOGin terms of economy.

In a method of producing an anisotropic electrically conductive film ofthe third mode of the present invention, by using a transfer body havinga columnar convex portion corresponding to a lattice point region of aplanar lattice pattern, formed on a surface thereof, electricallyconductive particles are deposited on a weak adhesive layer formed on atop surface of the convex portion, then the electrically conductiveparticles are transferred to an electrically insulating adhesive baselayer. Therefore, it is possible to achieve that a proportion of the“lattice points, at which no electrically conductive particle isdisposed” with respect to all the lattice points of the planar latticepattern assumed as the reference region of the anisotropic electricallyconductive film is 15% or less, and a proportion of “lattice pointshaving plural electrically conductive particles disposed in anaggregated state” to all the lattice points of the planar latticepattern is 10% or less, and moreover, the electrically conductiveparticles disposed in an aggregated state are aggregated with respect tothe plane direction of the anisotropic electrically conductive film.Thus, by using the method of production according to an embodiment ofthe present invention, it is possible to economically advantageouslyproduce an anisotropic electrically conductive film, and with theanisotropic electrically conductive film, it is possible to achieve ananisotropic conductive connection between an IC chip and a wiring board,wherein the pitches thereof are reduced while occurrence of a shortcircuit and a conduction failure are significantly suppressed.

In the anisotropic electrically conductive film of the fourth mode ofthe present invention, a proportion of the “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as the referenceregion is set to less than 10%, and a proportion of “lattice points atwhich plural electrically conductive particles are disposed in anaggregated state” is set to 15% or less, and moreover, at least some ofthe electrically conductive particles disposed in an aggregated stateare disposed with an oblique shift in a thickness direction of theanisotropic electrically conductive film. Therefore, when theanisotropic electrically conductive film according to an embodiment ofthe present invention is applied to an anisotropic conductiveconnection, it is possible to achieve a good initial conductivity and agood conduction reliability after aging, and it is also possible tosuppress occurrence of a short circuit. Furthermore, in addition to COG,it is excellent for electronic components having a relatively large bumparea and a distance between the bumps such as FOG in terms of economy.

In a method of producing the anisotropic electrically conductive film ofthe fourth mode of the present invention, by using a transfer bodyhaving a columnar convex portion corresponding to a lattice point regionof a planar lattice pattern, formed on a surface thereof, theelectrically conductive particles are deposited on the weak adhesivelayer formed on the top surface of the convex portion, then theelectrically conductive particles are transferred to the electricallyinsulating adhesive base layer. Therefore, it is possible to achievethat a proportion of the “lattice points, at which no electricallyconductive particle is disposed” with respect to all the lattice pointsof the planar lattice pattern assumed as the reference region of theanisotropic electrically conductive film is less than 10%, and aproportion of the “lattice points at which plural electricallyconductive particles are disposed in an aggregated state” with respectto all the lattice points of the planar lattice pattern is 15% or less,and moreover, at least some of electrically conductive particlesdisposed in an aggregated state are disposed with an oblique shift in athickness direction of the anisotropic electrically conductive film.Consequently, in the production method according to an embodiment of thepresent invention, it is possible to economically advantageously producean anisotropic electrically conductive film, and with the anisotropicelectrically conductive film, it is possible to achieve an anisotropicconductive connection between an IC chip and a wiring board wherein thepitches thereof are reduced while occurrence of a short circuit and aconduction failure are significantly suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of an anisotropic electricallyconductive film of a first mode of the present invention.

FIG. 2 is a perspective plan view of the anisotropic electricallyconductive film of the first mode of the present invention.

FIG. 3A is a step explanatory diagram of a method of producing theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 3B is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 3C is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 3D is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 3E is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 3F is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the first mode of thepresent invention while being a schematic cross-sectional view of theanisotropic electrically conductive film of the first mode of thepresent invention.

FIG. 4 is a cross-sectional view of an anisotropic electricallyconductive film of a second mode of the present invention.

FIG. 5A is a perspective plan view of the anisotropic electricallyconductive film of the second mode of the present invention.

FIG. 5B is a partially enlarged view of the perspective plan view of theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6A is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6B is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6C is a step explanatory diagram of the method of producing theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6D is a step explanatory diagram of the method of producing of theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6E is a step explanatory diagram of the method of producing of theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 6F is a step explanatory diagram of the method of producing of theanisotropic electrically conductive film of the second mode of thepresent invention while being a schematic cross-sectional view of theanisotropic electrically conductive film of the second mode of thepresent invention.

FIG. 7 is a cross-sectional view of an anisotropic electricallyconductive film of a third mode of the present invention.

FIG. 8 is a perspective plan view of the anisotropic electricallyconductive film of the third mode of the present invention.

FIG. 9A is a step explanatory diagram of a production method of theanisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 9B is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 9C is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 9D is a step explanatory diagram of the production method of ananisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 9E is a step explanatory diagram of the production method of ananisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 9F is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the third mode of thepresent invention while being a schematic cross-sectional view of theanisotropic electrically conductive film of the third mode of thepresent invention.

FIG. 10 is a cross-sectional view of the of an anisotropic electricallyconductive film of a fourth mode of the present invention.

FIG. 11 is a perspective plan view of the anisotropic electricallyconductive film of the fourth mode of the present invention.

FIG. 12A is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

FIG. 12B is a step explanatory diagram of a production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

FIG. 12C is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

FIG. 12D is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

FIG. 12E is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

FIG. 12F is a step explanatory diagram of the production method of theanisotropic electrically conductive film of the fourth mode of thepresent invention while being a schematic cross-sectional view of theanisotropic electrically conductive film of the fourth mode of thepresent invention.

DESCRIPTION OF EMBODIMENTS

An anisotropic electrically conductive film according to an embodimentof the present invention has a structure in which an electricallyinsulating adhesive base layer and an electrically insulating adhesivecover layer are laminated together, and near an interface therebetween,electrically conductive particles are disposed at the lattice points ofthe planar lattice pattern. In the anisotropic electrically conductivefilm, a proportion of the lattice points, at which no electricallyconductive particle is disposed with respect to all the lattice pointsof the planar lattice pattern assumed as a reference region (aproportion of the lattice points having “omission” of the electricallyconductive particle) is less than 20%, and a proportion of the latticepoints at which plural electrically conductive particles are disposed inan aggregated state with respect to all the lattice points of the planarlattice pattern (a proportion of the lattice points having “aggregation”of the electrically conductive particles) is 15% or less, and moreover,a sum of the omission and the aggregation is 25% or less. The referenceregion is a substantially square region including a side X and a side Yin a center portion of the anisotropic electrically conductive filmplane, the side X and the side Y satisfying the Relationships (A), (2),and (3). Here, D is an average particle diameter of the electricallyconductive particles, the side Y is a straight line disposed at an anglein a range of less than ±450 with respect to the longitudinal directionof the anisotropic electrically conductive film, and the side X is astraight line perpendicular to the side Y.100D≤X+Y≤400D  (A)X≥5D  (2)Y≥5D  (3)

An anisotropic electrically conductive film according to an embodimentof the present invention will be specifically described for each mode,below. Specifically, firstly, an anisotropic electrically conductivefilm and a production method thereof of a first mode of the presentinvention will be described in detail with reference to the drawings.

Anisotropic Electrically Conductive Film of First Mode

As illustrated in FIG. 1 (cross-sectional view) and FIG. 2 (perspectiveplan view), an anisotropic electrically conductive film 10 according toan embodiment of the present invention has a structure in which anelectrically insulating adhesive base layer 11 and an electricallyinsulating adhesive cover layer 12 are laminated together, and near aninterface therebetween, electrically conductive particles 13 aredisposed at the lattice points of the planar lattice pattern (dottedline in FIG. 2). In FIGS. 1 and 2, the planar lattice pattern is assumedto be along a longitudinal direction of the anisotropic electricallyconductive film 10 and a direction (short-side direction) that isorthogonal to the longitudinal direction; however, the entire patternmay be assumed to be inclined with respect to both the longitudinaldirection and the short-side direction. Here, an arrow A indicates aposition at which no electrically conductive particles are disposed atthe lattice points with a planar lattice, in other words, a position atwhich there is so-called “omission” of the electrically conductiveparticles. Note that an arrow B indicates a position at which theelectrically conductive particles are aggregated in contact with eachother, and an arrow C indicates a position at which the electricallyconductive particles are aggregated without contacting each other. Here,to “aggregate without contacting each other” means that the electricallyconductive particles are in close proximity in a range not exceeding 25%the average particle diameter of the electrically conductive particles.

“Omission” of Electrically Conductive Particle

In the anisotropic electrically conductive film according to anembodiment of the present invention, a proportion of “lattice points, atwhich no electrically conductive particles are disposed” (A in FIG. 2)(proportion of the lattice points at which an electrically conductiveparticle is not present) with respect to all the lattice points of theplanar lattice pattern assumed as any reference region of theanisotropic electrically conductive film is set to less than 20%,preferably to 18% or less, and more preferably to 10 to 18%. Thereby, ina case where the anisotropic electrically conductive film according toan embodiment of the present invention is applied to anisotropicconductive connection, it is possible to achieve good initialconductivity and good conduction reliability after aging, and it is alsopossible to suppress occurrence of a short circuit.

Planar Lattice Pattern

Examples of the planar lattice pattern include a rhombic lattice, ahexagonal lattice, a square lattice, a rectangular lattice, and aparallelotope lattice. In particular, the hexagonal lattice, in whichclosest packing is possible, is preferable.

Here, it is possible to select the whole surface of the anisotropicelectrically conductive film as the reference region of the anisotropicelectrically conductive film, but ordinarily, it is preferable toselect, as the reference region, a substantially square region includinga side X and a side Y in a center portion of the anisotropicelectrically conductive film plane, the side X and the side Y satisfyingthe following Relationship (A), and preferably satisfying the followingRelationships (1), (2), and (3).100D≤X+Y≤400D  (A)X+Y=100D  (1)X≥5D  (2)Y≥5D  (3)

Note that in a case of applying the film to FOG connection in which aconnection area is comparatively large, it is possible to reduce theamount of electrically conductive particles being present in the film.In such a case, as described below, it is preferable to increase each ofthe values of X and Y, preferably to 20D or greater, and it ispreferable to set a value of “X+Y” to a value from 100D to around 400Dand finally to 400D.X+Y=400DX≥20DY≥20D

In Relationships (A) and (1) to (3), and the above relationships, D isan average particle diameter of the electrically conductive particles.It is possible to measure the average particle diameter of theelectrically conductive particles by using an image-type or laser-typeparticle size analyzer. A surface observation can be used for such ameasurement. In addition, the side Y is a straight line disposed at anangle in a range of less than ±45° with respect to the longitudinaldirection (refer to FIG. 2) of the anisotropic electrically conductivefilm, and the side X is a straight line perpendicular to the side Y.

By defining the reference region in this manner, the reference regionmay resemble or approximate a shape of a bump to which the electricallyconductive particles are pressed. As a result, it is possible toincrease the permissible range of shift of the electrically conductiveparticles from the planar lattice pattern, and anisotropic conductiveconnection is economically and stably established. In other words, it ispossible to reliably establish anisotropic conductive connection becausethe electrically conductive particles are captured by any bump and thereis no excessive aggregation in a space between bumps, even if there maybe a shift, an omission or a contact of the electrically conductiveparticles in a range assumed to be in a range in which the smallest sideof the reference region is set to 5 times or greater of the electricallyconductive particle diameter.

Note that the reason that the smallest side is 5 times or greater of theelectrically conductive particle diameter is because it is necessary forthe side to be typically larger than the average particle diameter ofthe electrically conductive particles for reliably capturing theparticles in at least one side of the bump that is subjected toanisotropic conductive connection, and moreover, it is necessary todesirably provide a size 2 times or greater the average particlediameter of the electrically conductive particles for a space betweenbumps because of preventing a short circuit. In other words, the reasonis because when focusing on a circular electrically conductive particleas one reference, if an unexpected failure does not occur within aconcentric circle having a diameter of sum of the average particlediameter D and 4 times the size thereof (4D), that is 5D, then it isconsidered that the requirements described above can be satisfied. Inaddition, the reason is because a minimum distance between bumps in acase of a fine pitch is less than 4 times the electrically conductiveparticle diameter as an example.

Aggregation of Electrically Conductive Particles

In a case of the anisotropic electrically conductive film according toan embodiment of the present invention, a proportion of the latticepoints (B and C of FIG. 2) having plural electrically conductiveparticles disposed in an aggregated state with respect to all thelattice points of the planar lattice pattern is preferably 15% or lessand more preferably 5% or less. The proportion is theoretically mostpreferable to become 0%, thus it may be less than 0.1%. When theproportion of the lattice points of aggregated disposition is 5% orless, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied to theanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit. Here,the degree of aggregation of the electrically conductive particles withrespect to one lattice point is as small as possible from the viewpointof suppressing a short circuit and it is preferable not to exceed two.Note that as illustrated as C in FIG. 2, in the case where theaggregated electrically conductive particles are not in contact witheach other, the space between them is preferably within 25% of theaverage particle diameter of the electrically conductive particles, andmore preferably within 15%.

Note that, in the first mode, a sum of the omission and the aggregationis preferably less than 25%.

Arrangement of Electrically Conductive Particles

It is preferable that 11 or more electrically conductive particles areconsecutively disposed in a direction perpendicular to the longitudinaldirection of the film, and it is more preferable that 13 or moreelectrically conductive particles are consecutively disposed. This isbecause, when there is an absence of electrically conductive particlesin the longitudinal direction of the bump, there is a concern that thereis a failure to anisotropic conductive connection. In this case, it ispreferable that all of the three consecutive rows along the longitudinaldirection of the film satisfy the above condition, and it is morepreferable that all of the five consecutive rows satisfy the abovecondition. Thereby, the number of electrically conductive particlescaptured by the bump can be equal to a certain number or more, and it ispossible to achieve a stable anisotropic conductive connection.

When the electrically conductive particles are aggregated, it ispreferable that in the vicinity of an aggregation of the twoelectrically conductive particles, there are three or less sets ofelectrically conductive particles that are connected by two, and morepreferable that there are two sets or less, and even more preferablethat there is one set or less. This is because when aggregations of thetwo electrically conductive particles densely exist, it becomes a causeof occurrence of a short circuit.

In addition, it is preferable that absence of four or more consecutiveelectrically conductive particles in the longitudinal direction of thefilm and absence of four or more consecutive electrically conductiveparticles in the direction orthogonal to the longitudinal direction ofthe film do not intersect, it is more preferable that any of the absenceof the four or more consecutive electrically conductive particles is notadjacent to each other via one or more electrically conductive particlesbeing lattice points, and it is even more preferable that any of theconsecutive four or more absences is not adjacent to each other via twoor more electrically conductive particles being lattice points. Such anintersection of absence is not a problem even if up to three rowsintersect simultaneously with absence in one direction. This is becausewhen there is consecutive absence not more than three rows, theelectrically conductive particles in the vicinity thereof are capturedby a bump.

Note that, generally it is not preferable that plural regions havingconsecutive absences intersecting with one another in this way arepresent in the vicinity of one another. However, as long as ananisotropic conductive connection is established via arrangements of theelectrically conductive particles, the number of which is equal to ormore than the number of regions with absences, there is no problem inthe stability of the anisotropic conductive connection.

Particle Area Occupancy

In addition, it is effective when a particle area occupancy, withrespect to the area of the reference region of the anisotropicelectrically conductive film, of all electrically conductive particlespresent in the area is generally 0.15% or greater, preferably 0.35% orgreater, and more preferably 1.4% or greater in a case where a bump sizeor a distance between bumps is relatively large, as in the FOGconnection. An upper limit in this case is preferably 35% or less and ismore preferably 32% or less. Furthermore, in a case where the bump sizeor the distance between the bumps is relatively small (for example, COGconnection), the upper limit is preferably from 15 to 35%, and morepreferably from 16 to 20%. When the distance is in this range, even in acase where the anisotropic electrically conductive film according to anembodiment of the present invention is applied to anisotropic conductiveconnection, it is possible to achieve better initial conductivity andconduction reliability after aging, and it is also possible to furthersuppress occurrence of a short circuit. Here, the particle areaoccupancy is a proportion, with respect to an area S of a referenceregion, of an area occupied by all the electrically conductive particlespresent in the reference region. The area occupied by all theelectrically conductive particles is represented by (R/2)²×π×n wherein Ris the average particle diameter of the electrically conductiveparticles and n is the number of electrically conductive particles.Accordingly, the particle area occupancy is represented by the followingequation: particle area occupancy (%)=[{(R/2)²×π×πn}/S]×100.

Note that, the calculated particle area occupancy is 0.157% in a casewhere the average particle diameter of the electrically conductiveparticles is 2 μm, a number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 0.35325% in acase where the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 1.413% in a casewhere the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 2000/mm² (0.002/μm²), X=Y=200D,and X+Y=400D. In addition, the calculated particle area occupancy is35.325% in a case where the average particle diameter of theelectrically conductive particles is 30 μm, the number density is500/mm² (0.0005/μm²), X=Y=200D, and X+Y=400D.

Electrically Conductive Particles

It is possible to appropriately select and use any electricallyconductive particles used in a known anisotropic electrically conductivefilm. Examples of the electrically conductive particles include metalparticles such as nickel, copper, silver, gold, and palladium andmetal-coated resin particles, where the surface of resin particles suchas polyamide and polybenzoguanamine is coated with metal such as nickel.In addition, from the viewpoint of handling during production, theaverage particle diameter of the electrically conductive particles ispreferably from 1 to 30 μm, more preferably from 1 to 10 μm, andparticularly preferably from 2 to 6 μm. As described above, it ispossible to measure the average particle diameter of the electricallyconductive particles using the image-type particle size analyzer. Asurface observation can be used for such a measurement.

The amount of the electrically conductive particles present in theanisotropic electrically conductive film depends on the lattice pitch ofthe planar lattice pattern and the average particle diameter of theelectrically conductive particles, and ordinarily is from 300 to40000/mm².

Distance Between Adjacent Lattice Points

The distance between adjacent lattice points of a planar lattice patternthat is assumed for the anisotropic electrically conductive film ispreferably greater than 0.5 times, more preferably 1 time or greater,even more preferably from 1 to 20 times the average particle diameter ofthe electrically conductive particles. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit.

Electrically Insulating Adhesive Base Layer

As the electrically insulating adhesive base layer 11, it is possible toappropriately select and use a base layer used as an electricallyinsulating adhesive base layer in a known anisotropic electricallyconductive film. For example, it is possible to use a photoradicalpolymerizable resin layer including an acrylate compound andphotoradical polymerization initiator, a thermal radical polymerizableresin layer including an acrylate compound and a thermal radicalpolymerization initiator, a thermal cationic polymerizable resin layerincluding an epoxy compound and a thermal cationic polymerizationinitiator, a thermal anionic polymerizable resin layer including anepoxy compound and a thermal anionic polymerization initiator, and thelike, or a cured resin layer thereof. In addition, it is possible toappropriately select and include a silane coupling agent, a pigment, anantioxidant, an ultraviolet absorber, and the like in the resin layersas appropriate.

Note that the electrically insulating adhesive base layer 11 can beformed by depositing a film using a coating method and drying, andfurther curing, a coating composition including the resin as describedabove, or otherwise by forming the coating composition into a film usinga method known in advance.

The thickness of such an electrically insulating adhesive base layer 11is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Electrically Insulating Adhesive Cover Layer

As the electrically insulating adhesive cover layer 12, a cover layerused as an electrically insulating adhesive cover layer in a knownanisotropic electrically conductive film can be selected and used asappropriate. Alternatively, the cover layer formed from the samematerial as that of the electrically insulating adhesive base layer 11as described earlier can be also used.

Note that the electrically insulating adhesive cover layer 12 may beformed by using a coating method and drying, and further curing, acoating composition including the resin as described above, or otherwiseby forming a film using a known technique in advance.

The thickness of such an electrically insulating adhesive cover layer 12is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Furthermore, an electrically insulating filler such as silica fineparticles, alumina, and aluminum hydroxide may be added to theelectrically insulating adhesive base layer 11 or the electricallyinsulating adhesive cover layer 12 as necessary. The blending amount ofthe electrically insulating filler is preferably from 3 to 40 parts bymass per 100 parts by mass of resin included in the layers. Thereby,even when the electrically insulating adhesive layer is melted duringanisotropic conductive connection, it is possible to prevent theelectrically conductive particles 13 from moving unnecessarily by themelted resin.

Lamination of Electrically Insulating Adhesive Base Layer andElectrically Insulating Adhesive Cover Layer and Embedding ofElectrically Conductive Particles

Note that in a case where the electrically insulating adhesive baselayer 11 and the electrically insulating adhesive cover layer 12 arelaminated together with the electrically conductive particles 13 beinginterposed therebetween, it is possible to perform the lamination byusing a known technique. In this case, the electrically conductiveparticles 13 are present near the interface of the layers. Here,“present near the interface” indicates that a part of the electricallyconductive particles intrudes into one layer, and the remainder intrudesinto the other layer. Furthermore, the electrically conductive particlesmay be embedded into the electrically insulating adhesive base layer. Inthis case, the electrically insulating adhesive cover layer may beformed without lamination.

Production of Anisotropic Electrically Conductive Film of First Mode

Next, a method of producing an anisotropic electrically conductive film,according to the first mode of the present invention, which has astructure in which the electrically insulating adhesive base layer andthe electrically insulating adhesive cover layer are laminated together,and near an interface therebetween, electrically conductive particlesare disposed at the lattice points of the planar lattice pattern, willbe described. The production method has the following steps (i) to (v).Each step will be described in detail with reference to the drawings.Note that this production method is not limiting.

Step (i)

First, as illustrated in FIG. 3A, a transfer body 100 is prepared inwhich a columnar convex portion 101 corresponding to the lattice pointsof the planar lattice pattern is formed on the surface. Here, thecolumnar shape includes a cylindrical shape or prism shape (a triangularprism, a square prism, a hexagonal prism, and the like). This columnarshape includes a cone type. The columnar shape is preferably thecylindrical shape. The height of the convex portion 101 can bedetermined depending on a terminal pitch, a terminal width, a spacingwidth, the average particle diameter of the electrically conductiveparticles, and the like where anisotropic conductive connection shouldbe provided. And the height is preferably not less than 1.2 times andless than 2 times the average particle diameter of the electricallyconductive particles used. In addition, a full width at half height(width at a half height) of the convex portion 101 is preferably notless than 0.7 times and not greater than 1.3 times the average particlediameter of the electrically conductive particle. If the height andwidth are in this range, then an effect is obtained in which consecutiveoccurrence of shedding and omission is avoided.

Furthermore, the convex portion 101 has a flat top surface with aflatness that can promote stable deposition of the electricallyconductive particles.

*Specific Example of Transfer Body

The transfer body that should be prepared in the step (i) can beprepared by utilizing a well-known technique. For example, a transferbody can be prepared by processing a metal plate to prepare a master,which is then coated with a curable resin composition, followed bycuring. Specifically, a flat metal plate is cut and processed to preparea transfer body master formed with a concave portion corresponding to aconvex portion, and then a concave portion formation surface of themaster is coated with a resin composition that configures the transferbody followed by curing. Then the composition is separated from themaster to obtain the transfer body.

Step (ii)

Next, as illustrated in FIG. 3B, at least the top surface of the convexportions 101 of the transfer body 100 in which plural convex portions101 are formed with the planar lattice pattern on the surface is set asa weak adhesive layer 102.

*Weak Adhesive Layer of Transfer Body

The weak adhesive layer 102 is a layer that exhibits an adhesive force,by which it is possible to temporarily hold the electrically conductiveparticles until the electrically conductive particles are transferred tothe electrically insulating adhesive base layer configuring theanisotropic electrically conductive film. Such a weak adhesive layer 102is formed at least on the top surface of the convex portions 101.Accordingly, the entire convex portions 101 may be weakly adhesive. Thethickness of the weak adhesive layer 102 can be appropriately determineddepending on the material of the weak adhesive layer 102, the particlediameter of the electrically conductive particles, and the like. Inaddition, “weak adhesive” has a meaning of a weaker adhesive force thanthe electrically insulating adhesive base layer when the electricallyconductive particles are transferred to the electrically insulatingadhesive base layer.

For such a weak adhesive layer 102, a weak adhesive layer used in aknown anisotropic electrically conductive film can be used. For example,it is possible to form the weak adhesive layer by applying asilicone-based adhesive composition or an adhesive layer of the samematerial as in the electrically insulating adhesive base layer or theelectrically insulating adhesive cover layer on a top surface of theconvex portions 101.

Step (iii)

Next, as illustrated in FIG. 3C, the electrically conductive particles103 are deposited on the weak adhesive layer 102 of the convex portions101 of the transfer body 100. Specifically, the electrically conductiveparticles 103 are scattered from above the convex portions 101 of thetransfer body 100, the electrically conductive particles 103 that arenot deposited on the weak adhesive layer 102 may be blown away using ablower. Alternatively, the direction of the surface is reversed fromFIG. 3C, and the top surface of a projection may be deposited on asurface all over which the electrically conductive particles are laid.This is to avoid unnecessary stress applied to the electricallyconductive particles. It is easy to recover and reuse the electricallyconductive particles by only electrically conductive particles necessaryfor the arrangement being deposited on the top surface of theprojection. Thus, economic superiority is obtained in comparison with amethod, in which the electrically conductive particles are packed in anopening portion and removed later. Note that in a case of the method, inwhich the electrically conductive particles are packed in an openportion and removed later, there is a concern that unnecessary stress iseasily applied to the unpacked electrically conductive particles.

Note that in FIG. 3C, a width of the convex portion 101 in the left halfis adjusted to be narrower than that of the convex portion 101 in theright half. As a result, there may be a difference in aggregation modeof the electrically conductive particle 103 between in the left half andthe right half as illustrated in FIG. 3C.

Step (iv)

Next, as illustrated in FIG. 3D, when the electrically insulatingadhesive base layer 104 that should configure the anisotropicelectrically conductive film is overlapped and pressed on a surface at aside on which the electrically conductive particles 103 of the transferbody 100 are deposited, the electrically conductive particles 103 aretransferred to one side of the electrically insulating adhesive baselayer 104 (FIG. 3E). In this case, preferably the transfer body 100overlaps and presses the electrically insulating adhesive base layer 104such that the convex portions 101 face downward. This is because theelectrically conductive particles that are not stuck to the top surfaceof the convex portion are easily removed by being blown while facingdown.

Step (v)

As illustrated in FIG. 3F, the electrically insulating adhesive baselayer 104 to which the electrically conductive particles 103 aretransferred is laminated, from the electrically conductive particletransferred surface side, with the electrically insulating adhesivecover layer 105. Thereby, an anisotropic electrically conductive film200 according to an embodiment of the present invention is obtained.

Note that in this anisotropic electrically conductive film 200, thereare cases where at one lattice point of a planer lattice pattern, pluralconductive particles are disposed in an aggregated state in contact witheach other in a horizontal direction or in close proximity. This isbecause when depositing the electrically conductive particles on theweak adhesive layer of the convex portion of the transfer body, thewidth of the convex portion (width of the weak adhesive layer) and theaverage particle diameter of electrically conductive particles areroughly the same, thus presence of plural electrically conductiveparticles on one convex portion is unlikely; however, there is apossibility that excessive electrically conductive particles may bedeposited on the terminal portion of the weak adhesive layer or thosewhich have detached from the convex portion and failed to be blown offmay remain in the gap between convex portions of the transfer body.

Next, an anisotropic electrically conductive film and a method ofproducing the anisotropic electrically conductive film according to thesecond mode of the present invention will be described in detail withreference to the drawings.

Anisotropic Electrically Conductive Film of Second Mode

As illustrated in FIG. 4 (cross-sectional view), FIG. 5A, and FIG. 5B(perspective plan view), an anisotropic electrically conductive film 10according to an embodiment of the present invention has a structure inwhich an electrically insulating adhesive base layer 11 and anelectrically insulating adhesive cover layer 12 are laminated together,and near an interface therebetween, electrically conductive particles 13are disposed at the lattice points of the planar lattice pattern (dottedline in FIG. 5A and FIG. 5B). In FIGS. 4, 5A, and 5B, the planar latticepattern is assumed to be along a longitudinal direction of theanisotropic electrically conductive film 10 and a direction (short-sidedirection) that is orthogonal to the longitudinal direction; however,the entire pattern may be assumed to be inclined with respect to boththe longitudinal direction and the short-side direction. Here, an arrowA indicates a position at which no electrically conductive particle isdisposed at the lattice points of a planar lattice, and a position atwhich there is so-called “omission” of the electrically conductiveparticles. Note that an arrow B indicates a position at which theelectrically conductive particles are aggregated in contact with eachother (connected), and an arrow C indicates a position at which theelectrically conductive particles are aggregated without contacting eachother. Here, to “aggregate without contacting each other” means that theelectrically conductive particles are in close proximity in a range notexceeding 25% the average particle diameter of the electricallyconductive particles.

“Omission” of Electrically Conductive Particle

In the anisotropic electrically conductive film according to anembodiment of the present invention, a proportion of “lattice points, atwhich no electrically conductive particle is disposed” (A of FIG. 5A)(proportion of the lattice points at which an electrically conductiveparticle is not present) with respect to all the lattice points of theplanar lattice pattern assumed as any reference region of theanisotropic electrically conductive film is set to less than 5%,preferably 4% or less, and more preferably from 1 or more to 4% or less.Thereby, in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve goodinitial conductivity and good conduction reliability after aging, and itis also possible to suppress occurrence of a short circuit.

Planar Lattice Pattern

Examples of the planar lattice pattern include a rhombic lattice, ahexagonal lattice, a square lattice, a rectangular lattice, and aparallelotope lattice. In particular, the hexagonal lattice, in whichclosest packing is possible, is preferable.

Here, it is possible to select the whole surface of the anisotropicelectrically conductive film as the reference region of the anisotropicelectrically conductive film, but ordinarily, it is preferable toselect, as the reference region, a substantially square region includinga side X and a side Y in a center portion of the anisotropicelectrically conductive film plane, the side X and the side Y satisfyingthe following Relationship (A), and preferably satisfy the followingRelationships (1), (2), and (3).100D≤X+Y≤400D  (A)X+Y=100D  (1)X≥5D  (2)Y≥5D  (3)

Note that in a case of applying the film to FOG connection in which aconnection area is comparatively large, it is possible to reduce theamount of electrically conductive particles being present in the film.In such a case, as described below, it is preferable to increase each ofthe values of X and Y, preferably to 20D or greater, and it ispreferable to set a value of “X+Y” to a value from 100D to around 400Dand finally to 400D.X+Y=400DX≥20DY≥20D

In Relationships (A) and (1) to (3), and the above relationships, D isan average particle diameter of the electrically conductive particles.It is possible to measure the average particle diameter of theelectrically conductive particles by using an image-type or laser-typeparticle size analyzer. A surface observation can be used for such ameasurement. In addition, the side Y is a straight line disposed at anangle in a range of less than ±45° with respect to the longitudinaldirection (refer to FIG. 5A) of the anisotropic electrically conductivefilm, and the side X is a straight line perpendicular to the side Y.

By defining the reference region in this manner, the reference regionmay resemble or approximate a shape of a bump to which the electricallyconductive particles are pressed. As a result, it is possible toincrease the permissible range of shift of the electrically conductiveparticles from the planar lattice pattern, and anisotropic conductiveconnection is economically and stably established. In other words, it ispossible to reliably establish anisotropic conductive connection becausethe electrically conductive particles are captured by any bump and thereis no excessive aggregation in a space between bumps, even if there maybe a shift, an omission or a contact of the electrically conductiveparticles in a range assumed to be in a range in which the smallest sideof the reference region is set to 5 times or greater of the electricallyconductive particle diameter.

Note that the reason that the smallest side is 5 times or greater of theelectrically conductive particle diameter is because it is necessary forthe side to be typically larger than the average particle diameter ofthe electrically conductive particles for reliably capturing theparticles in at least one side of the bump that is subjected toanisotropic conductive connection, and moreover, it is necessary todesirably provide a size 2 times or greater the average particlediameter of the electrically conductive particles for a space betweenbumps because of preventing a short circuit. In other words, the reasonis because when focusing on a circular electrically conductive particleas one reference, if an unexpected failure does not occur within aconcentric circle having a diameter of sum of the average particlediameter D and 4 times the size thereof (4D), that is 5D, then it isconsidered that the requirements described above can be satisfied. Inaddition, the reason is because a minimum distance between bumps in acase of a fine pitch is less than 4 times the electrically conductiveparticle diameter as an example.

Aggregation of Electrically Conductive Particles

Furthermore, in the anisotropic electrically conductive film accordingto an embodiment of the present invention, a proportion of the latticepoints with plural electrically conductive particles disposed in anaggregated state with respect to all the lattice points of the planarlattice pattern (arrows B and C in FIG. 5A) is preferably 15% or less,may be greater than 10% and less than 15%, and as long as it is from 11or more to 14% or less, there is no practical problem. When theproportion of the lattice points of aggregated disposition is withinthis range, even in a case where the anisotropic electrically conductivefilm according to an embodiment of the present invention is applied tothe anisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit. Here, astate in which the electrically conductive particles are aggregatedincludes not only a case where the electrically conductive particles aredirectly connected as indicated by an arrow B of FIG. 5A but also a casewhere the electrically conductive particles are in extreme proximity toone another though not connected directly as indicated by an arrow C ofFIG. 5A. The spacing of the above mentioned proximity is preferablywithin 25% of the average particle diameter of the electricallyconductive particles. Furthermore, the degree of aggregation of theelectrically conductive particles with respect to a single latticepoint, although it is possible to have cases where more than twoelectrically conductive particles are connected in a chain, but from theviewpoint of suppressing short circuits, is preferable to be small, andit is preferable that more than two electrically conductive particles donot aggregate.

Note that in this second mode, a sum of the omission and the aggregationis preferably less than 20%.

In the present invention, the aggregation direction of the electricallyconductive particles disposed in an aggregated state (normally, adirection of a line connecting the centroids of each of the twoaggregated electrically conductive particles) is shifted in a thicknessdirection, thus becomes inclined with respect to the plane direction ofthe anisotropic electrically conductive film as in the arrows B and C ofFIG. 4. In order not to disrupt pressing during connection, the degreeof inclination is preferably between 5° to 45°, more preferably between10° to 40°. Note that the reason that such inclination occurs is becauseit is possible to capture electrically conductive particles by only oneside when it is present at the terminal portion of the bump at the timeof connection (pressing is affected if overlapping without inclination).Note that there is no particular problem even if the aggregation is in ahorizontal direction.

Arrangement of Electrically Conductive Particles

It is preferable that 11 or more electrically conductive particles areconsecutively disposed in a direction perpendicular to the longitudinaldirection of the film, and it is more preferable that 13 or moreelectrically conductive particles are consecutively disposed. This isbecause, when there is an absence of electrically conductive particlesin the longitudinal direction of the bump, there is a concern that thereis a failure to anisotropic conductive connection. In this case, it ispreferable that all of the three consecutive rows along the longitudinaldirection of the film satisfy the above condition, and it is morepreferable that all of the five consecutive rows satisfy the abovecondition. Thereby, the number of electrically conductive particlescaptured by the bump can be equal to a certain number or more, and it ispossible to achieve a stable anisotropic conductive connection.

When the electrically conductive particles are aggregated, it ispreferable that in the vicinity of an aggregation of the twoelectrically conductive particles, there are three or less sets ofelectrically conductive particles that are connected by two, and morepreferable that there are two sets or less, and even more preferablethat there is one set or less. This is because when aggregations of thetwo electrically conductive particles densely exist, it becomes a causeof occurrence of a short circuit. It is preferable that the aggregationsof the two electrically conductive particles are within threeconsecutive sets in one direction of the arrangement while satisfyingthe above mentioned conditions.

In addition, it is preferable that absence of four or more consecutiveelectrically conductive particles in the longitudinal direction of thefilm and absence of four or more consecutive electrically conductiveparticles in the direction orthogonal to the longitudinal direction ofthe film do not intersect, it is more preferable that any of the absenceof the four or more consecutive electrically conductive particles is notadjacent to each other via one or more electrically conductive particlesbeing lattice points, and it is even more preferable that any of theconsecutive four or more absences is not adjacent to each other via twoor more electrically conductive particles being lattice points. Such anintersection of absence is not a problem even if up to three rowsintersect simultaneously with absence in one direction. This is becausewhen there is consecutive absence not more than three rows, theelectrically conductive particles in the vicinity thereof are capturedby a bump.

Note that, generally it is not preferable that plural regions havingconsecutive absences intersecting with one another in this manner arepresent in the vicinity of one another. However, as long as ananisotropic conductive connection is established via arrangements of theelectrically conductive particles, the number of which is equal to ormore than the number of regions with absences, there is no problem inthe stability of the anisotropic conductive connection.

In addition, as illustrated in FIG. 5B, from the viewpoint ofsuppressing short circuits, it is preferable that a distance L between alattice point P1 in which the aggregated electrically conductiveparticles 13 are disposed and a center P2 of a circle inscribing theaggregated electrically conductive particles 13 is 25% or less withrespect to the average particle diameter of electrically conductiveparticles.

Particle Area Occupancy

In addition, it is effective when a particle area occupancy, withrespect to the area of any reference region of the anisotropicelectrically conductive film, of all electrically conductive particlespresent in the area is generally 0.15% or greater, preferably 0.35% orgreater, and more preferably 1.4% or greater in a case where a bump sizeor a distance between bumps is relatively large, as in the FOGconnection. An upper limit in this case is preferably 35% or less and ismore preferably 32% or less. Furthermore, in a case where the bump sizeor the distance between bumps is relatively small (for example, COGconnection), the upper limit is even more preferably from 15 to 35%, andparticularly preferably from 20 to 25%. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit. Here,the particle area occupancy is a proportion of an area that allelectrically conductive particles occupy which are present in anyreference region with respect to an area S of the reference region. Thearea occupied by all the electrically conductive particles isrepresented by (R/2)²×π×n wherein R is the average particle diameter ofthe electrically conductive particles and n is the number ofelectrically conductive particles. Accordingly, the particle areaoccupancy is represented by the following equation: particle areaoccupancy (%)=[{(R/2)²×π×n}/S]×100.

Note that, the calculated particle area occupancy is 0.157% in a casewhere the average particle diameter of the electrically conductiveparticles is 2 μm, a number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 0.35325% in acase where the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 1.413% in a casewhere the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 2000/mm² (0.002/μm²), X=Y=200D,and X+Y=400D. In addition, the calculated particle area occupancy is35.325% in a case where the average particle diameter of theelectrically conductive particles is 30 μm, the number density is500/mm² (0.0005/μm²), X=Y=200D, and X+Y=400D.

Electrically Conductive Particles

It is possible to appropriately select and use any electricallyconductive particles used in a known anisotropic electrically conductivefilm. Examples of the electrically conductive particles include metalparticles such as nickel, copper, silver, gold, and palladium andmetal-coated resin particles, where the surface of resin particles suchas polyamide and polybenzoguanamine is coated with metal such as nickel.Furthermore, from the viewpoint of handling during production, theaverage particle diameter of the electrically conductive particles ispreferably from 1 to 30 μm, more preferably from 1 to 10 μm, andparticularly preferably from 2 to 6 μm. As described above, it ispossible to measure the average particle diameter of the electricallyconductive particles by using an image-type or laser-type particle sizeanalyzer.

The amount of the electrically conductive particles present in theanisotropic electrically conductive film depends on the lattice pitch ofthe planar lattice pattern and the average particle diameter of theelectrically conductive particles, and ordinarily is from 300 to40000/mm².

Distance Between Adjacent Lattice Points

The distance between adjacent lattice points of a planar lattice patternthat is assumed for the anisotropic electrically conductive film ispreferably greater than 0.5 times, more preferably 1 time or greater,even more preferably from 1 to 20 times the average particle diameter ofthe electrically conductive particles. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit.

Electrically Insulating Adhesive Base Layer

As the electrically insulating adhesive base layer 11, it is possible toappropriately select and use a base layer used as an electricallyinsulating adhesive base layer in a known anisotropic electricallyconductive film. For example, it is possible to use a photoradicalpolymerizable resin layer including an acrylate compound andphotoradical polymerization initiator, a thermal radical polymerizableresin layer including an acrylate compound and a thermal radicalpolymerization initiator, a thermal cationic polymerizable resin layerincluding an epoxy compound and a thermal cationic polymerizationinitiator, a thermal anionic polymerizable resin layer including anepoxy compound and a thermal anionic polymerization initiator, and thelike, or a curable resin layer thereof. In addition, it is possible toappropriately select and include a silane coupling agent, a pigment, anantioxidant, an ultraviolet absorber, and the like in the resin layersas appropriate.

Note that the electrically insulating adhesive base layer 11 can beformed by depositing a film using a coating method and drying, andfurther curing, a coating composition including the resin as describedabove, or otherwise by forming the coating composition into a film usinga method known in advance.

The thickness of such an electrically insulating adhesive base layer 11is preferably 1 to 30 μm and more preferably 2 to 15 μm.

Electrically Insulating Adhesive Cover Layer

As the electrically insulating adhesive cover layer 12, a cover layerused as an electrically insulating adhesive cover layer in a knownanisotropic electrically conductive film can be selected and used asappropriate. Alternatively, the cover layer formed from the samematerial as that of the electrically insulating adhesive base layer 11as described earlier can be also used.

Note that the electrically insulating adhesive cover layer 12 may beformed by using a coating method and drying, and further curing, acoating composition including the resin as described above, or otherwiseby forming a film using a known technique in advance.

The thickness of such an electrically insulating adhesive cover layer 12is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Furthermore, an electrically insulating filler such as silica fineparticles, alumina, and aluminum hydroxide may be added to theelectrically insulating adhesive base layer 11 or the electricallyinsulating adhesive cover layer 12 as necessary. The blending amount ofthe electrically insulating filler is preferably from 3 to 40 parts bymass per 100 parts by mass of resin that configures the layers. Thereby,even when the electrically insulating adhesive layer is melted duringanisotropic conductive connection, it is possible to prevent theelectrically conductive particles 13 from moving unnecessarily by themelted resin.

Lamination of Electrically Insulating Adhesive Base Layer andElectrically Insulating Adhesive Cover Layer and Embedding ofElectrically Conductive Particles

Note that in a case where the electrically insulating adhesive baselayer 11 and the electrically insulating adhesive cover layer 12 arelaminated together interposing the electrically conductive particles 13therebetween, it is possible to perform the process by using a knownmethod. In this case, the electrically conductive particles 13 arepresent near the interface of the layers. Here, “present near theinterface” indicates that a part of the electrically conductiveparticles intrudes into one layer, and the remainder intrudes into theother layer. Furthermore, the electrically conductive particles may beembedded into the electrically insulating adhesive base layer. In thiscase, the electrically insulating adhesive cover layer may be formedwithout lamination.

Production of Anisotropic Electrically Conductive Film of Second Mode

Next, a method of producing an anisotropic electrically conductive film,according to a second mode of the present invention, which has astructure in which the electrically insulating adhesive base layer andthe electrically insulating adhesive cover layer are laminated together,and near an interface therebetween, electrically conductive particlesare disposed at the lattice points of the planar lattice pattern, willbe described. The production method has the following steps (i) to (v).Each step will be described in detail with reference to the drawings.Note that this production method is not limiting.

Step (i)

First, as illustrated in FIG. 6A, a transfer body 100 is prepared inwhich a columnar convex portion 101 corresponding to the lattice pointsof the planar lattice pattern is formed on the surface. This columnarshape includes a cone type. The columnar shape is preferably thecylindrical shape. The height of the convex portion 101 can bedetermined depending on a terminal pitch, a terminal width, a spacingwidth, the average particle diameter of the electrically conductiveparticles, and the like where anisotropic conductive connection shouldbe provided. And the height is preferably not less than 2 times and lessthan 4 times the average particle diameter of the electricallyconductive particles used. Furthermore, a full width at the half heightof the convex portion 101 (width at a half height) is preferably notless than 1.4 times and not greater than 3.6 times the average particlediameter of electrically conductive particles. If the height and thewidth are within these ranges, then an effect is obtained whereoccurrence of excess omission is prevented and omission is generatedonly sporadically.

Furthermore, the convex portion 101 has a substantially flat top surfacewith a flatness that can promote stable deposition of the electricallyconductive particles.

*Specific Example of Transfer Body

The transfer body that should be prepared in the step (i) can beprepared by utilizing a well-known technique. For example, a transferbody can be prepared by processing a metal plate to prepare a master,which is then coated with a curable resin composition, followed bycuring. Specifically, a flat metal plate is cut and processed to preparea transfer body master formed with a concave portion corresponding to aconvex portion, and then a concave portion formation surface of themaster is coated with a resin composition that configures the transferbody followed by curing. Then the composition is separated from themaster to obtain the transfer body.

Step (ii)

Next, as illustrated in FIG. 6B, at least the top surface of the convexportions 101 of the transfer body 100 in which plural convex portions101 are formed with the planar lattice pattern on the surface is set asa weak adhesive layer 102.

*Weak Adhesive Layer of Transfer Body

The weak adhesive layer 102 is a layer that exhibits an adhesive force,by which it is possible to temporarily hold the electrically conductiveparticles until the electrically conductive particles are transferred tothe electrically insulating adhesive base layer configuring theanisotropic electrically conductive film. Such a weak adhesive layer 102is formed at least on the top surface of the convex portions 101.Accordingly, the entire convex portions 101 may be slightly adhesive.The thickness of the weak adhesive layer 102 can be appropriatelydetermined depending on the material of the weak adhesive layer 102, theparticle diameter of the electrically conductive particles, and thelike. In addition, “weak adhesive” has a meaning of a weaker adhesiveforce than the electrically insulating adhesive base layer when theelectrically conductive particles are transferred to the electricallyinsulating adhesive base layer.

For such a weak adhesive layer 102, a weak adhesive layer used in aknown anisotropic electrically conductive film can be used. For example,it is possible to form the weak adhesive layer by applying asilicone-based adhesive composition or an adhesive layer of the samematerial as in the electrically insulating adhesive base layer or theelectrically insulating adhesive cover layer on a top surface of theconvex portions 101.

Step (iii)

Next, as illustrated in FIG. 6C, the electrically conductive particles103 are deposited on the weak adhesive layer 102 of the convex portions101 of the transfer body 100. Specifically, the electrically conductiveparticles 103 are scattered from above the convex portions 101 of thetransfer body 100, the electrically conductive particles 103 that arenot deposited on the weak adhesive layer 102 may be blown away using ablower. In this case, the electrically conductive particles aredeposited on a side surface of some of the convex portions 101 at acertain frequency due to an action of static electricity and the like,and some electrically conductive particles may not be removed by ablower.

Note that the direction of the surface may be reversed from FIG. 6C, andthe top surface of the projection may be attached to a surface overwhich the electrically conductive particles are all laid. This is toavoid unnecessary stress applied to the electrically conductiveparticles. It is easy to recover and reuse the electrically conductiveparticles by only electrically conductive particles necessary for thearrangement being deposited on the top surface of the projection. Thus,economic superiority is obtained in comparison with a method, in whichthe electrically conductive particles are packed in an opening portionand removed later. Note that in a case of the method for packing andtaking out the electrically conductive particles in an opening, there isa concern that it is easy for unnecessary stress to be applied to theelectrically conductive particles that are not packed.

Note that in FIG. 6C, a width of the weak adhesive layer 102 of theconvex portion 101 in the left half is adjusted to be narrower than thatof the weak adhesive layer 102 of the convex portion 101 in the righthalf. As a result, between left half and right half, as illustrated inFIG. 6C, differences in aggregation mode of the electrically conductiveparticle 103 may occur.

Step (iv)

Next, as illustrated in FIG. 6D, when the electrically insulatingadhesive base layer 104 that should configure the anisotropicelectrically conductive film is overlapped and pressed on a surface at aside on which the electrically conductive particles 103 of the transferbody 100 are deposited, the electrically conductive particles 103 aretransferred to one side of the electrically insulating adhesive baselayer 104 (FIG. 6E). In this case, preferably the transfer body 100overlaps and presses the electrically insulating adhesive base layer 104such that the convex portions 101 face downward. This is because theelectrically conductive particles that are not stuck to the top surfaceof the convex portion are easily removed by being blown while facingdown.

Step (v)

As illustrated in FIG. 6F, the electrically insulating adhesive coverlayer 105 is laminated on the electrically insulating adhesive baselayer 104, on which the electrically conductive particles 103 aretransferred, from a side, on which the electrically conductive particlesare transferred. Thereby, an anisotropic electrically conductive film200 according to an embodiment of the present invention is obtained.

Next, an anisotropic electrically conductive film and a method ofproducing the anisotropic electrically conductive film according to thethird mode of the present invention will be described in detail withreference to the drawings.

Anisotropic Electrically Conductive Film of Third Mode

As illustrated in FIG. 7 (cross-sectional view) and FIG. 8 (perspectiveplan view), an anisotropic electrically conductive film 10 according toan embodiment of the present invention has a structure in which anelectrically insulating adhesive base layer 11 and an electricallyinsulating adhesive cover layer 12 are laminated together, and near aninterface therebetween, electrically conductive particles 13 aredisposed at the lattice points of the planar lattice pattern (dottedline in FIG. 8). In FIGS. 7 and 8, the planar lattice pattern is assumedto be along a longitudinal direction of the anisotropic electricallyconductive film 10 and a direction (short-side direction) that isorthogonal to the longitudinal direction; however, the entire patternmay be assumed to be inclined with respect to both the longitudinaldirection and the short-side direction. Here, an arrow A indicates aposition at which no electrically conductive particle is disposed at thelattice points with a planar lattice, and a position at which there isso-called “omission” of the electrically conductive particles. Note thatan arrow B indicates a position at which electrically conductiveparticles are in contact with each other and are aggregated.

“Omission” of Electrically Conductive Particle

In the anisotropic electrically conductive film according to anembodiment of the present invention, a proportion of “lattice points, atwhich no electrically conductive particle is disposed” (A in FIG. 8)(proportion of the lattice points at which an electrically conductiveparticle is not present) with respect to all the lattice points of theplanar lattice pattern assumed as the reference region of theanisotropic electrically conductive film is set to 15% or less,preferably to 10% or less, and more preferably to from 6 to 10%.Thereby, in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve goodinitial conductivity and good conduction reliability after aging, and itis also possible to suppress occurrence of a short circuit.

Planar Lattice Pattern

Examples of the planar lattice pattern include a rhombic lattice, ahexagonal lattice, a square lattice, a rectangular lattice, and aparallelotope lattice. In particular, the hexagonal lattice, in whichclosest packing is possible, is preferable.

Here, it is possible to select the whole surface of the anisotropicelectrically conductive film as the reference region of the anisotropicelectrically conductive film, but ordinarily, it is preferable toselect, as the reference region, a substantially square region includinga side X and a side Y in a center portion of the anisotropicelectrically conductive film plane, the side X and the side Y satisfyingthe following Relationship (A) and preferably satisfy the followingRelationships (1), (2), and (3).100D≤X+Y≤400D  (A)X+Y=100D  (1)X≥5D  (2)Y≥5D  (3)

Note that in a case of applying the film to FOG connection in which aconnection area is comparatively large, it is possible to reduce theamount of electrically conductive particles being present in the film.In such a case, as described below, it is preferable to increase each ofthe values of X and Y, preferably to 20D or greater, and it ispreferable to set a value of “X+Y” to a value from 100D to around 400Dand finally to 400D.X+Y=400DX≥20DY≥20D

In Relationships (A) and (1) to (3), and the above relationships, D isan average particle diameter of the electrically conductive particles.It is possible to measure the average particle diameter of theelectrically conductive particles by using an image-type or laser-typeparticle size analyzer. A surface observation can be used for such ameasurement. Furthermore, the side Y is a straight line disposed at anangle in a range of less than ±45° with respect to the longitudinaldirection (refer to FIG. 8) of the anisotropic electrically conductivefilm, and the side X is a straight line perpendicular to the side Y.

By defining the reference region in this manner, the reference regionmay resemble or approximate a shape of a bump to which the electricallyconductive particles are pressed. As a result, it is possible toincrease the permissible range of shift of the electrically conductiveparticles from the planar lattice pattern, and anisotropic conductiveconnection is economically and stably established. In other words, it ispossible to reliably establish anisotropic conductive connection becausethe electrically conductive particles are captured by any bump and thereis no excessive aggregation in a space between bumps, even if there maybe a shift, an omission or a contact of the electrically conductiveparticles in a range assumed to be in a range in which the smallest sideof the reference region is set to 5 times or greater of the electricallyconductive particle size.

Note that the reason that the smallest side is 5 times or greater of theelectrically conductive particle diameter is because it is necessary forthe side to be typically larger than the average particle diameter ofthe electrically conductive particles for reliably capturing theparticles in at least one side of the bump that is subjected toanisotropic conductive connection, and moreover, it is necessary todesirably provide a size 2 times or greater the average particlediameter of the electrically conductive particles for a space betweenbumps because of preventing a short circuit. In other words, the reasonis because when focusing on a circular electrically conductive particleas one reference, if an unexpected failure does not occur within aconcentric circle having a diameter of sum of the average particlediameter D and 4 times the size thereof (4D), that is 5D, then it isconsidered that the requirements described above can be satisfied. Inaddition, the reason is because a minimum distance between bumps in acase of a fine pitch is less than 4 times the electrically conductiveparticle diameter as an example.

Aggregation of Electrically Conductive Particles

In addition, in the anisotropic electrically conductive film accordingto an embodiment of the present invention, a proportion of the latticepoints at which plural electrically conductive particles are disposed inan aggregated state with respect to all the lattice points of the planarlattice pattern (B of FIG. 8) is 10% or less, preferably 9% or less, andfrom 5 to 9% as a range with no practical problem. When the proportionof the lattice points of aggregated disposition is within this range,even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied to theanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit. Here,the degree of aggregation of the electrically conductive particles withrespect to one lattice point is as small as possible from the viewpointof suppressing a short circuit and it is preferable not to exceed two.

Note that in this third mode, a sum of the omission and the aggregationis preferably 25% or less.

Arrangement of Electrically Conductive Particles

It is preferable that 11 or more electrically conductive particles areconsecutively disposed in a direction perpendicular to the longitudinaldirection of the film, and it is more preferable that 13 or moreelectrically conductive particles are consecutively disposed. This isbecause, when there is an absence of electrically conductive particlesin the longitudinal direction of the bump, there is a concern that thereis a failure to anisotropic conductive connection. In this case, it ispreferable that all of the three consecutive rows along the longitudinaldirection of the film satisfy the above condition, and it is morepreferable that all of the five consecutive rows satisfy the abovecondition. Thereby, the number of electrically conductive particlescaptured by the bump can be equal to a certain number or more, and it ispossible to achieve a stable anisotropic conductive connection.

When the electrically conductive particles are aggregated, it ispreferable that in the vicinity of an aggregation of the twoelectrically conductive particles, there are three or less sets ofelectrically conductive particles that are connected by two, and morepreferable that there are two sets or less, and even more preferablethat there is one set or less. This is because when aggregations of thetwo electrically conductive particles densely exist, it becomes a causeof occurrence of a short circuit.

In addition, it is preferable that absence of four or more consecutiveelectrically conductive particles in the longitudinal direction of thefilm and absence of four or more consecutive electrically conductiveparticles in the direction orthogonal to the longitudinal direction ofthe film do not intersect, it is more preferable that any of the absenceof the four or more consecutive electrically conductive particles is notadjacent to each other via one or more electrically conductive particlesbeing lattice points, and it is even more preferable that any of theconsecutive four or more absences is not adjacent to each other via twoor more electrically conductive particles being lattice points. Such anintersection of absence is not a problem even if up to three rowsintersect simultaneously with absence in one direction. This is becausewhen there is consecutive absence not more than three rows, theelectrically conductive particles in the vicinity thereof are capturedby a bump.

Note that, generally it is not preferable that plural regions havingconsecutive absences intersecting with one another in this manner arepresent in the vicinity of one another. However, as long as ananisotropic conductive connection is established via arrangements of theelectrically conductive particles, the number of which is equal to orgreater than the number of regions with absences, there is no problem inthe stability of the anisotropic conductive connection. Specifically, aslong as there are one or more electrically conductive particlesconnected by two, on a 7×7 matrix around the region of absence as thecenter, there is no practical problem.

Particle Area Occupancy

In addition, it is effective when a particle area occupancy, withrespect to the area of the reference region of the anisotropicelectrically conductive film, of all electrically conductive particlespresent in the area is generally 0.15% or greater, preferably 0.35% orgreater, and more preferably 1.4% or greater in a case where a bump sizeor a distance between bumps is relatively large, as in the FOGconnection. An upper limit in this case is preferably 35% or less and ismore preferably 32% or less. In a case where the bump size or thedistance between the bumps is relatively small (for example, COGconnection), the upper limit is more preferably from 15 to 35%, andparticularly preferably from 16 to 20%. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit. Here,the particle area occupancy is a proportion, with respect to an area Sof a reference region, of an area occupied by all the electricallyconductive particles present in the reference region. The area occupiedby all the electrically conductive particles is represented by(R/2)²×π×n wherein R is the average particle diameter of theelectrically conductive particles and n is the number of electricallyconductive particles. Accordingly, the particle area occupancy isrepresented by the following equation: particle area occupancy(%)=[{(R/2)²×π×n}/S]×100.

Note that, the calculated particle area occupancy is 0.157% in a casewhere the average particle diameter of the electrically conductiveparticles is 2 μm, a number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 0.35325% in acase where the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 1.413% in a casewhere the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 2000/mm² (0.002/μm²), X=Y=200D,and X+Y=400D. In addition, the calculated particle area occupancy is35.325% in a case where the average particle diameter of theelectrically conductive particles is 30 μm, the number density is500/mm² (0.0005/μm²), X=Y=200D, and X+Y=400D.

Electrically Conductive Particles

It is possible to appropriately select and use any electricallyconductive particles used in a known anisotropic electrically conductivefilm. Examples of the electrically conductive particles include metalparticles such as nickel, copper, silver, gold, and palladium andmetal-coated resin particles, where the surface of resin particles suchas polyamide and polybenzoguanamine is coated with metal such as nickel.Furthermore, from the viewpoint of handling during production, theaverage particle diameter of the electrically conductive particles ispreferably from 1 to 30 μm, more preferably from 1 to 10 μm, and morepreferably from 2 to 6 μm. As described above, it is possible to measurethe average particle diameter of the electrically conductive particlesby using an image-type or laser-type particle size analyzer.

The amount of the electrically conductive particles present in theanisotropic electrically conductive film depends on the lattice pitch ofthe planar lattice pattern and the average particle diameter of theelectrically conductive particles, and ordinarily, is from 300 to40000/mm².

Distance Between Adjacent Lattice Points

The distance between adjacent lattice points of a planar lattice patternthat is assumed for the anisotropic electrically conductive film ispreferably greater than 0.5 times, more preferably 1 time or greater,even more preferably from 1 to 20 times the average particle diameter ofthe electrically conductive particles. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit.

Electrically Insulating Adhesive Base Layer

As the electrically insulating adhesive base layer 11, it is possible toappropriately select and use a base layer used as an electricallyinsulating adhesive base layer in a known anisotropic electricallyconductive film. For example, it is possible to use a photoradicalpolymerizable resin layer including an acrylate compound andphotoradical polymerization initiator, a thermal radical polymerizableresin layer including an acrylate compound and a thermal radicalpolymerization initiator, a thermal cationic polymerizable resin layerincluding an epoxy compound and a thermal cationic polymerizationinitiator, a thermal anionic polymerizable resin layer including anepoxy compound and a thermal anionic polymerization initiator, and thelike, or a curable resin layer thereof. In addition, it is possible toappropriately select and include a silane coupling agent, a pigment, anantioxidant, an ultraviolet absorber, and the like in the resin layersas appropriate.

Note that the electrically insulating adhesive base layer 11 can beformed by depositing a film using a coating method and drying, andfurther curing, a coating composition including the resin as describedabove, or otherwise by forming the coating composition into a film usinga method known in advance.

The thickness of such an electrically insulating adhesive base layer 11is preferably from 1 to 30 μm and more preferably from 2 to 15 Gm.

Electrically Insulating Adhesive Cover Layer

As the electrically insulating adhesive cover layer 12, a cover layerused as an electrically insulating adhesive cover layer in a knownanisotropic electrically conductive film can be selected and used asappropriate. Alternatively, the cover layer formed from the samematerial as that of the electrically insulating adhesive base layer 11as described earlier can be also used.

Note that the electrically insulating adhesive cover layer 12 may beformed by using a coating method and drying, and further curing, acoating composition including the resin as described above, or otherwiseby forming a film using a known technique in advance.

The thickness of such an electrically insulating adhesive cover layer 12is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Furthermore, an electrically insulating filler such as silica fineparticles, alumina, and aluminum hydroxide may be added to theelectrically insulating adhesive base layer 11 or the electricallyinsulating adhesive cover layer 12 as necessary. The blending amount ofthe electrically insulating filler is preferably 3 to 40 parts by massper 100 parts by mass of resin included in the layers. Thereby, evenwhen the electrically insulating adhesive layer is melted duringanisotropic conductive connection, it is possible to prevent theelectrically conductive particles 13 from moving unnecessarily by themelted resin.

Lamination of Electrically Insulating Adhesive Base Layer andElectrically Insulating Adhesive Cover Layer and Embedding ofElectrically Conductive Particles

Note that in a case where the electrically insulating adhesive baselayer 11 and the electrically insulating adhesive cover layer 12 arelaminated together interposing the electrically conductive particles 13therebetween, it is possible to perform the process by using a knownmethod. In this case, the electrically conductive particles 13 arepresent near the interface of the layers. Here, “present near theinterface” indicates that a part of the electrically conductiveparticles intrudes into one layer, and the remainder intrudes into theother layer. Furthermore, the electrically conductive particles may beembedded into the electrically insulating adhesive base layer. In thiscase, the electrically insulating adhesive cover layer may be formedwithout lamination.

Production of Anisotropic Electrically Conductive Film of Third Mode

Next, a method of producing an anisotropic electrically conductive film,according to the third mode of the present invention, which has astructure in which the electrically insulating adhesive base layer andthe electrically insulating adhesive cover layer are laminated together,and near an interface therebetween, electrically conductive particlesare disposed at the lattice points of the planar lattice pattern, willbe described. The production method has the following steps (i) to (v).Each step will be described in detail with reference to the drawings.Note that this production method is not limiting.

Step (i)

First, as illustrated in FIG. 9A, a transfer body 100, a surface ofwhich is formed with a convex portion 101 corresponding to the latticepoints of a planar lattice pattern is prepared. Here, as the shape ofthe convex portion 101, a columnar form (cylinder, triangular prism,square prism, hexagonal prism and the like, for example), roughlycolumnar, hemispherical, truncated cone, truncated pyramid and the likemay be mentioned. The height of the convex portion 101 can be determineddepending on a terminal pitch, a terminal width, a spacing width, theaverage particle diameter of the electrically conductive particles, andthe like where anisotropic conductive connection should be provided. Andthe height is preferably not less than 1.2 times and less than 2 timesthe average particle diameter of the electrically conductive particlesused. Furthermore, a full width at the half height of the convex portion101 (width at a half height) is preferably not less than 1.4 times andnot greater than 3.6 times the average particle diameter of electricallyconductive particles. If the height and width are in this range, then aneffect is obtained in which consecutive occurrence of shedding andomission is avoided.

Furthermore, the convex portion 101 has a flat top surface with aflatness that can promote stable deposition of the electricallyconductive particles.

*Specific Example of Transfer Body

The transfer body that should be prepared in the step (i) can beprepared by utilizing a well-known technique. For example, a transferbody can be prepared by processing a metal plate to prepare a master,which is then coated with a curable resin composition, followed bycuring. Specifically, a flat metal plate is cut and processed to preparea transfer body master formed with a concave portion corresponding to aconvex portion, and then a concave portion formation surface of themaster is coated with a resin composition that configures the transferbody followed by curing. Then the composition is separated from themaster to obtain the transfer body.

Step (ii)

Next, as illustrated in FIG. 9B, at least the top surface of the convexportions 101 of the transfer body 100 in which plural convex portions101 are formed with the planar lattice pattern on the surface is set asa weak adhesive layer 102.

*Weak Adhesive Layer of Transfer Body

The weak adhesive layer 102 is a layer that exhibits an adhesive force,by which it is possible to temporarily hold the electrically conductiveparticles until the electrically conductive particles are transferred tothe electrically insulating adhesive base layer configuring theanisotropic electrically conductive film. Such a weak adhesive layer 102is formed at least on the top surface of the convex portions 101.Accordingly, the entire convex portions 101 may be slightly adhesive.The thickness of the weak adhesive layer 102 can be appropriatelydetermined depending on the material of the weak adhesive layer 102, theparticle diameter of the electrically conductive particles, and thelike. In addition, “weak adhesive” has a meaning of a weaker adhesiveforce than the electrically insulating adhesive base layer when theelectrically conductive particles are transferred to the electricallyinsulating adhesive base layer.

For such a weak adhesive layer 102, a weak adhesive layer used in aknown anisotropic electrically conductive film can be used. For example,it is possible to form the weak adhesive layer by applying asilicone-based adhesive composition and an adhesive layer of the samematerial as in the electrically insulating adhesive base layer or theelectrically insulating adhesive cover layer on a top surface of theconvex portions 101.

Step (iii)

Next, as illustrated in FIG. 9C, the electrically conductive particles103 are deposited on the weak adhesive layer 102 of the convex portions101 of the transfer body 100. Specifically, the electrically conductiveparticles 103 are scattered from above the convex portions 101 of thetransfer body 100, the electrically conductive particles 103 that arenot deposited on the weak adhesive layer 102 may be blown away using ablower. In this case, the electrically conductive particles aredeposited on a side surface of some of the convex portions 101 at acertain frequency due to an action of static electricity and the like,and some electrically conductive particles may not be removed by ablower.

Note that the direction of the surface may be reversed from FIG. 9C, andthe top surface of the projection may be attached to a surface overwhich the electrically conductive particles are all laid. This is toavoid unnecessary stress applied to the electrically conductiveparticles. It is easy to recover and reuse the electrically conductiveparticles by only electrically conductive particles necessary for thearrangement being deposited on the top surface of the projection. Thus,economic superiority is obtained in comparison with a method, in whichthe electrically conductive particles are packed in an opening portionand removed later. Note that in a case of the method for packing andtaking out the electrically conductive particles in an opening, there isa concern that it is easy for unnecessary stress to be applied to theelectrically conductive particles that are not packed.

Step (iv)

Next, as illustrated in FIG. 9D, when the electrically insulatingadhesive base layer 104 that should configure the anisotropicelectrically conductive film is overlapped and pressed on a surface at aside on which the electrically conductive particles 103 of the transferbody 100 are deposited, the electrically conductive particles 103 aretransferred to one side of the electrically insulating adhesive baselayer 104 (FIG. 9E). In this case, preferably the transfer body 100overlaps and presses the electrically insulating adhesive base layer 104such that the convex portions 101 face downward. This is because theelectrically conductive particles that are not stuck to the top surfaceof the convex portion are easily removed by being blown while facingdown.

Step (v)

As illustrated in FIG. 9F, the electrically insulating adhesive coverlayer 105 is laminated on the electrically insulating adhesive baselayer 104, on which the electrically conductive particles 103 aretransferred, from a side, on which the electrically conductive particlesare transferred. Thereby, an anisotropic electrically conductive film200 according to an embodiment of the present invention is obtained.

Note that in the anisotropic electrically conductive film 200, whenplural conductive particles are disposed at one lattice point of aplaner lattice pattern, these electrically conductive particles aredisposed in contact with each other in a horizontal direction. This isto prevent excessive decrease in the particle number density.

Next, an anisotropic electrically conductive film and a productionmethod thereof according to the fourth mode of the present inventionwill be described in detail with reference to the drawings.

Anisotropic Electrically Conductive Film of Fourth Mode

As illustrated in FIG. 10 (cross-sectional view) and FIG. 11(perspective plan view), an anisotropic electrically conductive film 10according to an embodiment of the present invention has a structure inwhich an electrically insulating adhesive base layer 11 and anelectrically insulating adhesive cover layer 12 are laminated together,and near an interface therebetween, electrically conductive particles 13are disposed at the lattice points of the planar lattice pattern (dottedline in FIG. 11). In FIGS. 10 and 11, the planar lattice pattern isassumed to be along a longitudinal direction of the anisotropicelectrically conductive film 10 and a direction that is orthogonal tothe longitudinal direction (short-side direction), however, the entirepattern may be assumed to be inclined with respect to both thelongitudinal direction and the short-side direction. Here, an arrow Aindicates a position at which no electrically conductive particle isdisposed at the lattice points with a planar lattice, and a position atwhich there is so-called “omission” of the electrically conductiveparticles. Note that an arrow B indicates a position at which theelectrically conductive particles are aggregated without contacting eachother. Here, to “aggregate without contacting each other” means that theelectrically conductive particles are in close proximity in a range notexceeding 50% of the average particle diameter of the electricallyconductive particles.

“Omission” of Electrically Conductive Particle

In the anisotropic electrically conductive film according to anembodiment of the present invention, a proportion of “lattice points, atwhich no electrically conductive particle is disposed” (A in FIG. 11)(proportion of the lattice points at which electrically conductiveparticles are not present) with respect to all the lattice points of theplanar lattice pattern assumed as the reference region of theanisotropic electrically conductive film is set to less than 10%, andpreferably to 6% or less. Thereby, in a case where the anisotropicelectrically conductive film according to an embodiment of the presentinvention is applied to anisotropic conductive connection, it ispossible to achieve good initial conductivity and good conductionreliability after aging, and it is also possible to suppress occurrenceof a short circuit.

Planar Lattice Pattern

Examples of the planar lattice pattern include a rhombic lattice, ahexagonal lattice, a square lattice, a rectangular lattice, and aparallelotope lattice. In particular, the hexagonal lattice, in whichclosest packing is possible, is preferable.

Here, it is possible to select the whole surface of the anisotropicelectrically conductive film as the reference region of the anisotropicelectrically conductive film, but ordinarily, it is preferable toselect, as the reference region, a substantially square region includinga side X and a side Y in a center portion of the anisotropicelectrically conductive film plane, the side X and the side Y satisfyingthe following Relationship (A) and preferably satisfy the followingRelationships (1), (2), and (3).100D≤X+Y≤400D  (A)X+Y=100D  (1)X≥5D  (2)Y≥5D  (3)

Note that in a case of applying the film to FOG connection in which aconnection area is comparatively large, it is possible to reduce theamount of electrically conductive particles being present in the film.In such a case, as described below, it is preferable to increase each ofthe values of X and Y, preferably to 20D or greater, and it ispreferable to set a value of “X+Y” to a value from 100D to around 400Dand finally to 400D.X+Y=400DX≥20DY≥20D

In Relationships (A) and (1) to (3), and the above relationships, D isan average particle diameter of the electrically conductive particles.It is possible to measure the average particle diameter of theelectrically conductive particles by using an image-type or laser-typeparticle size analyzer. A surface observation can be used for such ameasurement. In addition, the side Y is a straight line disposed at anangle in a range of less than +45° with respect to the longitudinaldirection (refer to FIG. 11) of the anisotropic electrically conductivefilm, and the side X is a straight line perpendicular to the side Y.

By defining the reference region in this manner, the reference regionmay resemble or approximate a shape of a bump to which the electricallyconductive particles are pressed. As a result, it is possible toincrease the permissible range of shift of the electrically conductiveparticles from the planar lattice pattern, and anisotropic conductiveconnection is economically and stably established. In other words, it ispossible to reliably establish anisotropic conductive connection becausethe electrically conductive particles are captured by any bump and thereis no excessive aggregation in a space between bumps, even if there maybe a shift, an omission or a contact of the electrically conductiveparticles in a range assumed to be in a range in which the smallest sideof the reference region is set to 5 times or greater of the electricallyconductive particle diameter.

Note that the reason that the smallest side is 5 times or greater of theelectrically conductive particle diameter is because it is necessary forthe side to be typically larger than the average particle diameter ofthe electrically conductive particles for reliably capturing theparticles in at least one side of the bump that is subjected toanisotropic conductive connection, and moreover, it is necessary todesirably provide a size 2 times or greater the average particlediameter of the electrically conductive particles for a space betweenbumps because of preventing a short circuit. In other words, the reasonis because when focusing on a circular electrically conductive particleas one reference, if an unexpected failure does not occur within aconcentric circle having a diameter of sum of the average particlediameter D and 4 times the size thereof (4D), that is 5D, then it isconsidered that the requirements described above can be satisfied. Inaddition, the reason is because a minimum distance between bumps in acase of a fine pitch is less than 4 times the electrically conductiveparticle diameter as an example.

Aggregation of Electrically Conductive Particles

In a case of the anisotropic electrically conductive film according toan embodiment of the present invention, a proportion of the latticepoints (B of FIG. 11) having plural electrically conductive particlesdisposed in an aggregated state with respect to all the lattice pointsof the planar lattice pattern is preferably 15% or less, more preferably11% or less, and even more preferably 9% or less. When the proportion ofthe lattice points of aggregated disposition is within this range, evenin a case where the anisotropic electrically conductive film accordingto an embodiment of the present invention is applied to the anisotropicconductive connection, it is possible to achieve better initialconductivity and conduction reliability after aging, and it is alsopossible to further suppress occurrence of a short circuit. Here, thedegree of aggregation of the electrically conductive particles withrespect to one lattice point is as small as possible from the viewpointof suppressing a short circuit and it is preferable not to exceed two.Note that there is no particular problem even if the aggregation is in ahorizontal direction.

Note that as a mode of the aggregation of the electrically conductiveparticles, as in an arrow B of FIGS. 10 and 11, at least some ofelectrically conductive particles are disposed in an aggregated statewith an oblique shift in a thickness direction of the anisotropicelectrically conductive film without being in contact with each other.Here, the term “with an oblique shift” means the electrically conductiveparticles are separated in an oblique direction in a cross sectionalview. From this, it is possible to achieve a state in which pressing isnot inhibited during the time of connection. Furthermore, when theelectrically conductive particles disposed with an oblique shift in thethickness direction is viewed in a planar view, the electricallyconductive particles appear to be partially overlapping as illustratedin FIG. 11. Thus, even if the resin flow occurs at the time ofconnection, anisotropic conductive connection may be achieved in any ofthe electrically conductive particles.

In addition, the distance between the electrically conductive particlesdisposed with an oblique shift in the thickness direction (aggregationdistance) is preferably from 25 to 50% the average particle diameter ofelectrically conductive particles and more preferably from 30 to 45%.Within this range, even if the electrically conductive particles are inthe terminal end during the time of connection, it is possible toachieve an effect where the contact with the electrically conductiveparticles present between the terminals is easily avoided. Thus, whenthe condition that does not adversely affect the connection is found, itis possible to relax restrictions on production conditions, and to haveboth performance and productivity.

Note that in the fourth mode, a sum of the omission and the aggregationis preferably less than 25%.

Arrangement of Electrically Conductive Particles

It is preferable that 11 or more electrically conductive particles areconsecutively disposed in a direction perpendicular to the longitudinaldirection of the film, and it is more preferable that 13 or moreelectrically conductive particles are consecutively disposed. This isbecause, when there is an absence of electrically conductive particlesin the longitudinal direction of the bump, there is a concern that thereis a failure to anisotropic conductive connection. In this case, it ispreferable that all of the three consecutive rows along the longitudinaldirection of the film satisfy the above condition, and it is morepreferable that all of the five consecutive rows satisfy the abovecondition. Thereby, the number of electrically conductive particlescaptured by the bump can be equal to a certain number or more, and it ispossible to achieve a stable anisotropic conductive connection. The rowalong longitudinal direction satisfies above mentioned conditions aslong as five or more electrically conductive particles overlap in thedirection perpendicular to the longitudinal direction.

When the electrically conductive particles are aggregated, it ispreferable that in the vicinity of an aggregation of the twoelectrically conductive particles, there are three or less sets ofelectrically conductive particles that are connected by two, and morepreferable that there are two sets or less, and even more preferablethat there is one set or less. This is because when aggregations of thetwo electrically conductive particles densely exist, it becomes a causeof occurrence of a short circuit.

In addition, it is preferable that absence of four or more consecutiveelectrically conductive particles in the longitudinal direction of thefilm and absence of four or more consecutive electrically conductiveparticles in the direction orthogonal to the longitudinal direction ofthe film do not intersect, it is more preferable that any of the absenceof the four or more consecutive electrically conductive particles is notadjacent to each other via one or more electrically conductive particlesbeing lattice points, and it is even more preferable that any of theconsecutive four or more absences is not adjacent to each other via twoor more electrically conductive particles being lattice points. Such anintersection of absence is not a problem even if up to three rowsintersect simultaneously with absence in one direction. This is becausewhen there is consecutive absence not more than three rows, theelectrically conductive particles in the vicinity thereof are capturedby a bump.

Note that, generally it is not preferable that plural regions havingconsecutive absences intersecting with one another in this manner arepresent in the vicinity of one another. However, as long as ananisotropic conductive connection is established via arrangements of theelectrically conductive particles, the number of which is equal to ormore than the number of regions with absences, there is no problem inthe stability of the anisotropic conductive connection. Aggregations ofthe two electrically conductive particles can exist adjacent to theregion intersecting to the consecutive absences.

Particle Area Occupancy

In addition, it is effective when a particle area occupancy, withrespect to the area of the reference region of the anisotropicelectrically conductive film, of all electrically conductive particlespresent in the area is generally 0.15% or greater, preferably 0.35% orgreater, and more preferably 1.4% or greater in a case where a bump sizeor a distance between bumps is relatively large, as in the FOGconnection. An upper limit in this case is preferably 35% or less and ismore preferably 32% or less. Even in a case where the bump size or thedistance between bumps is relatively small (for example, COGconnection), the upper limit is preferably 35% or less, more preferably32% or less, even more preferably 25% or less, and particularlypreferably from 18 to 23%. When the distance is in this range, even in acase where the anisotropic electrically conductive film according to anembodiment of the present invention is applied to anisotropic conductiveconnection, it is possible to achieve better initial conductivity andconduction reliability after aging, and it is also possible to furthersuppress occurrence of a short circuit. Here, the particle areaoccupancy is a proportion, with respect to an area S of a referenceregion, of an area occupied by all the electrically conductive particlespresent in the reference region. The area that all electricallyconductive particles occupy is represented by (R/2)²×π×n wherein R isthe average particle diameter of the electrically conductive particlesand n is the number of electrically conductive particles. Accordingly,the particle area occupancy is represented by the following equation:particle area occupancy (%)=[{(R/2)²×π×n}/S]×100.

Note that, the calculated particle area occupancy is 0.157% in a casewhere the average particle diameter of the electrically conductiveparticles is 2 μm, a number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 0.35325% in acase where the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 500/mm² (0.0005/μm²), X=Y=200D,and X+Y=400D. The calculated particle area occupancy is 1.413% in a casewhere the average particle diameter of the electrically conductiveparticles is 3 μm, the number density is 2000/mm² (0.002 μm²), X=Y=200D,and X+Y=400D. In addition, the calculated particle area occupancy is35.325% in a case where the average particle diameter of theelectrically conductive particles is 30 μm, the number density is500/mm² (0.0005/μm²), X=Y=200D, and X+Y=400D.

Electrically Conductive Particles

It is possible to appropriately select and use any electricallyconductive particles used in a known anisotropic electrically conductivefilm. Examples of the electrically conductive particles include metalparticles such as nickel, copper, silver, gold, and palladium andmetal-coated resin particles, where the surface of resin particles suchas polyamide and polybenzoguanamine is coated with metal such as nickel.Furthermore, from the viewpoint of handling during production, theaverage particle diameter of the electrically conductive particles ispreferably from 1 to 30 μm, more preferably from 1 to 10 μm, and morepreferably from 2 to 6 μm. As described above, it is possible to measurethe average particle diameter of the electrically conductive particlesby using an image-type or laser-type particle size analyzer.

The amount of the electrically conductive particles present in theanisotropic electrically conductive film depends on the lattice pitch ofthe planar lattice pattern and the average particle diameter of theelectrically conductive particles, and ordinarily is from 300 to40000/mm².

Distance Between Adjacent Lattice Points

The distance between adjacent lattice points of a planar lattice patternthat is assumed for the anisotropic electrically conductive film ispreferably greater than 0.5 times, more preferably 1 time or greater,even more preferably from 1 to 20 times the average particle diameter ofthe electrically conductive particles. When the distance is in thisrange, even in a case where the anisotropic electrically conductive filmaccording to an embodiment of the present invention is applied toanisotropic conductive connection, it is possible to achieve betterinitial conductivity and conduction reliability after aging, and it isalso possible to further suppress occurrence of a short circuit.

Electrically Insulating Adhesive Base Layer

As the electrically insulating adhesive base layer 11, it is possible toappropriately select and use a base layer used as an electricallyinsulating adhesive base layer in a known anisotropic electricallyconductive film. For example, it is possible to use a photoradicalpolymerizable resin layer including an acrylate compound andphotoradical polymerization initiator, a thermal radical polymerizableresin layer including an acrylate compound and a thermal radicalpolymerization initiator, a thermal cationic polymerizable resin layerincluding an epoxy compound and a thermal cationic polymerizationinitiator, a thermal anionic polymerizable resin layer including anepoxy compound and a thermal anionic polymerization initiator, and thelike, or a curable resin layer thereof. In addition, it is possible toappropriately select and include a silane coupling agent, a pigment, anantioxidant, an ultraviolet absorber, and the like in the resin layersas appropriate.

Note that the electrically insulating adhesive base layer 11 can beformed by depositing a film using a coating method and drying, andfurther curing, a coating composition including the resin as describedabove, or otherwise by forming the coating composition into a film usinga method known in advance.

The thickness of such an electrically insulating adhesive base layer 11is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Electrically Insulating Adhesive Cover Layer

As the electrically insulating adhesive cover layer 12, a cover layerused as an electrically insulating adhesive cover layer in a knownanisotropic electrically conductive film can be selected and used asappropriate. Alternatively, the cover layer formed from the samematerial as that of the electrically insulating adhesive base layer 11as described earlier can be also used.

Note that the electrically insulating adhesive cover layer 12 may beformed by using a coating method and drying, and further curing, acoating composition including the resin as described above, or otherwiseby forming a film using a known technique in advance.

The thickness of such an electrically insulating adhesive cover layer 12is preferably from 1 to 30 μm and more preferably from 2 to 15 μm.

Furthermore, an electrically insulating filler such as silica fineparticles, alumina, and aluminum hydroxide may be added to theelectrically insulating adhesive base layer 11 or the electricallyinsulating adhesive cover layer 12 as necessary. The blending amount ofthe electrically insulating filler is preferably 3 to 40 parts by massper 100 parts by mass of resin included in the layers. Thereby, evenwhen the electrically insulating adhesive layer is melted duringanisotropic conductive connection, it is possible to prevent theelectrically conductive particles 13 from moving unnecessarily by themelted resin.

Lamination of Electrically Insulating Adhesive Base Layer andElectrically Insulating Adhesive Cover Layer and Embedding ofElectrically Conductive Particles

Note that in a case where the electrically insulating adhesive baselayer 11 and the electrically insulating adhesive cover layer 12 arelaminated together with the electrically conductive particles 13 beinginterposed therebetween, it is possible to perform the lamination byusing a known technique. In this case, the electrically conductiveparticles 13 are present near the interface of the layers. Here,“present near the interface” indicates that a part of the electricallyconductive particles intrudes into one layer, and the remainder intrudesinto the other layer. Furthermore, the electrically conductive particlesmay be embedded into the electrically insulating adhesive base layer. Inthis case, the electrically insulating adhesive cover layer may beformed without lamination.

Production of Anisotropic Electrically Conductive Film of Fourth Mode

Next, a method of producing an anisotropic electrically conductive film,according to the fourth mode of the present invention, which has astructure in which the electrically insulating adhesive base layer andthe electrically insulating adhesive cover layer are laminated together,and near an interface therebetween, electrically conductive particlesare disposed at the lattice points of the planar lattice pattern, willbe described. The production method has the following steps (i) to (v).Each step will be described in detail with reference to the drawings.Note that this production method is not limiting.

Step (i)

First, as illustrated in FIG. 12A, a transfer body 100 is prepared inwhich a columnar convex portion 101 corresponding to the lattice pointsof the planar lattice pattern is formed on the surface. Here, thecolumnar shape includes a cylindrical shape or prism shape (a triangularprism, a square prism, a hexagonal prism, and the like). This columnarshape includes a cone type. The columnar shape is preferably thecylindrical shape. The height of the convex portion 101 can bedetermined depending on a terminal pitch, a terminal width, a spacingwidth, the average particle diameter of the electrically conductiveparticles, and the like where anisotropic conductive connection shouldbe provided. And the height is preferably not less than 2 times and lessthan 4 times the average particle diameter of the electricallyconductive particles used. In addition, a full width at half height(width at a half height) of the convex portion 101 is preferably notless than 0.7 times and not greater than 1.3 times the average particlediameter of the electrically conductive particle. If the height andwidth are in this range, then an effect is obtained in which consecutiveoccurrence of shedding and omission is avoided.

Furthermore, the convex portion 101 has a flat top surface with aflatness that can promote stable deposition of the electricallyconductive particles.

*Specific Example of Transfer Body

The transfer body that should be prepared in the step (i) can beprepared by utilizing a well-known technique. For example, a transferbody can be prepared by processing a metal plate to prepare a master,which is then coated with a curable resin composition, followed bycuring. Specifically, a flat metal plate is cut and processed to preparea transfer body master formed with a concave portion corresponding to aconvex portion, and then a concave portion formation surface of themaster is coated with a resin composition that configures the transferbody followed by curing. Then the composition is separated from themaster to obtain the transfer body.

Step (ii)

Next, as illustrated in FIG. 12B, at least the top surface of the convexportions 101 of the transfer body 100 in which plural convex portions101 are formed with the planar lattice pattern on the surface is set asa weak adhesive layer 102.

*Weak Adhesive Layer of Transfer Body

The weak adhesive layer 102 is a layer that exhibits an adhesive force,by which it is possible to temporarily hold the electrically conductiveparticles until the electrically conductive particles are transferred tothe electrically insulating adhesive base layer configuring theanisotropic electrically conductive film. Such a weak adhesive layer 102is formed at least on the top surface of the convex portions 101.Accordingly, the entire convex portions 101 may be slightly adhesive.The thickness of the weak adhesive layer 102 can be appropriatelydetermined depending on the material of the weak adhesive layer 102, theparticle diameter of the electrically conductive particles, and thelike. In addition, “weak adhesive” has a meaning of a weaker adhesiveforce than the electrically insulating adhesive base layer when theelectrically conductive particles are transferred to the electricallyinsulating adhesive base layer.

For such a weak adhesive layer 102, a weak adhesive layer used in aknown anisotropic electrically conductive film can be used. For example,it is possible to form the weak adhesive layer by applying asilicone-based adhesive composition and an adhesive layer of the samematerial as in the electrically insulating adhesive base layer or theelectrically insulating adhesive cover layer on a top surface of theconvex portions 101.

Step (iii)

Next, as illustrated in FIG. 12C, the electrically conductive particles103 are deposited on the weak adhesive layer 102 of the convex portions101 of the transfer body 100. Specifically, the electrically conductiveparticles 103 are scattered from above the convex portions 101 of thetransfer body 100, the electrically conductive particles 103 that arenot deposited on the weak adhesive layer 102 may be blown away using ablower. In this case, the electrically conductive particles aredeposited on a side surface of some of the convex portions 101 at acertain frequency due to an action of static electricity and the like,and some electrically conductive particles may not be removed by ablower.

Note that the direction of the surface may be reversed from FIG. 12C,and the top surface of the projection may be attached to a surface overwhich the electrically conductive particles are all laid. This is toavoid unnecessary stress applied to the electrically conductiveparticles. It is easy to recover and reuse the electrically conductiveparticles by only electrically conductive particles necessary for thearrangement being deposited on the top surface of the projection. Thus,economic superiority is obtained in comparison with a method, in whichthe electrically conductive particles are packed in an opening portionand removed later. Note that in a case of the method for packing andtaking out the electrically conductive particles in an opening, there isa concern that it is easy for unnecessary stress to be applied to theelectrically conductive particles that are not packed.

Step (iv)

Next, as illustrated in FIG. 12D, when the electrically insulatingadhesive base layer 104 that should configure the anisotropicelectrically conductive film is overlapped and pressed on a surface at aside on which the electrically conductive particles 103 of the transferbody 100 are deposited, the electrically conductive particles 103 aretransferred to one side of the electrically insulating adhesive baselayer 104 (FIG. 12E). In this case, preferably the transfer body 100overlaps and presses the electrically insulating adhesive base layer 104such that the convex portions 101 face downward. This is because theelectrically conductive particles that are not stuck to the top surfaceof the convex portion are easily removed by being blown while facingdown.

Step (v)

As illustrated in FIG. 12F, the electrically insulating adhesive coverlayer 105 is laminated on the electrically insulating adhesive baselayer 104, on which the electrically conductive particles 103 aretransferred, from a side, on which the electrically conductive particlesare transferred. Thereby, an anisotropic electrically conductive film200 according to an embodiment of the present invention is obtained.

Noted that in the anisotropic electrically conductive film 200, theelectrically conductive particles that are still deposited on the sidesurface of the convex portion 101 in the step (iii) would be theelectrically conductive particles that are aggregated in a thicknessdirection of the anisotropic electrically conductive film 200 if theelectrically conductive particles 103 are present in the weak adhesivelayer 102 of the convex portion 101. Furthermore, if the electricallyconductive particles 103 are not present in the weak adhesive layer 102of the convex portion 101, the electrically conductive particles will bedisposed with a shift in a horizontal and a thickness direction from thelattice point.

Connection Structural Body

The anisotropic electrically conductive film according to the first,second, third, or fourth mode of the present invention may be disposedbetween a terminal (such as a bump) of a first electronic component(such as an IC chip) and a terminal (such as a bump or a pad) of asecond electronic component (such as a wiring board), and finally curedby using thermocompression bonding from the first or second electroniccomponent side to perform anisotropic conductive connection. Then aconnection structural body, in which a short circuit or a conductionfailure is suppressed, of a so-called chip on glass (COG), film on glass(FOG), or the like can be obtained.

EXAMPLES

The anisotropic electrically conductive film of the first mode of thepresent invention will be specifically described, below.

Example 1A

A nickel plate having a thickness of 2 mm was prepared, and acylindrically-shaped concave portion (an inner diameter 5 μm and depth 6μm) was formed in a tetragonal lattice pattern. Thus, the transfer bodymaster was obtained. The distance between the centers of adjacentconcave portions was 8 μm. Accordingly, the density of concave portionswas 16000/mm².

The resultant transfer body master was coated with a photopolymerizableresin composition containing 60 parts by mass of phenoxy resin (YP-50,Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylateresin (M208, Toagosei Co., Ltd.), and 2 parts by mass ofphotopolymerization initiator (IRGACURE184, BASF Japan Ltd.) on a PET(polyethylene terephthalate) film to a dried thickness of 30 μm, andafter drying for five minutes at 80° C., light irradiation at 1000 mJwas performed by a high pressure mercury lamp. Thus, the transfer bodywas created.

The transfer body was peeled off from the master, and wound on astainless steel roll with a diameter of 20 cm so that the convexportions were on the outer side. Then, the roll was brought into contactwith an adhesive sheet obtained by impregnating a nonwoven fabric with aweak adhesive composition containing 70 parts by mass of epoxy resin(jER828, Mitsubishi Chemical Corporation) and 30 parts by mass ofphenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) whilerotating the roll. Next, the weak adhesive composition was deposited onthe top surface of the convex portions to form the weak adhesive layerwith a thickness of 1 μm. Thus, the transfer body was obtained.

The electrically conductive particles with an average particle diameterof 4 μm (nickel plated resin particles (AUL704, Sekisui Chemical Co.,Ltd.)) were scattered on the surface of the transfer body, andsubsequently, the electrically conductive particles, which were notdeposited to the weak adhesive layer, were removed by blowing.

The transfer body, to which the electrically conductive particles weredeposited, was pressed, at a temperature of 50° C. and with a pressureof 0.5 MPa, from the side on which electrically conductive particleswere deposited, against a sheet-shaped thermosetting-type electricallyinsulating adhesive film with a thickness of 5 μm that is theelectrically insulating adhesive base layer (a film formed from anelectrically insulating adhesive composition containing 60 parts by massof phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 40parts by mass of epoxy resin (jER828, Mitsubishi Chemical Corporation),2 parts by mass of cationic curing agent (SI-60L, Sanshin ChemicalIndustry Co., Ltd.), and 20 parts by mass of silica fine particles(Aerosil RY200, Nippon Aerosil Co., Ltd.)). Thus, the electricallyconductive particles were transferred to the electrically insulatingadhesive base layer.

On the side of the electrically insulating adhesive base layer obtained,on which the electrically conductive particles were deposited, anothersheet-shaped electrically insulating adhesive film with a thickness of15 μm (film formed from an insulating adhesive composition containing 60parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin ChemicalCo., Ltd.), 40 parts by mass of epoxy resin (jER828, Mitsubishi ChemicalCorporation), and 2 parts by mass of cationic curing agent (SI-60L,Sanshin Chemical Industry Co., Ltd.)) was overlapped as a transparentelectrically insulating adhesive cover layer and laminated together at atemperature of 60° C. and with a pressure of 2 MPa. Thereby, theanisotropic electrically conductive film was obtained.

Example 2A

Other than doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 1A, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1A.

Example 3A

Except for setting the inner diameter of the concave portions of thetransfer body master to 3.6 μm, setting a distance between the centersof adjacent concave portions to 6 μm, so that the density of the concaveportions is 28000/mm², and using electrically conductive particles(AUL703, Sekisui Chemical Co., Ltd.) having an average particle diameterof 3 μm instead of electrically conductive particles having an averageparticle diameter of 4 μm, the anisotropic electrically conductive filmwas obtained by repeating the steps of Example 1A.

Example 4A

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 3A, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 3A.

Comparative Example 1A

Except for setting the depth of the concave portion of the transfer bodymaster to 4.4 μm, the inner diameter of the concave portion to 4.8 μm,and setting the distance between the centers of the adjacent concaveportions to be 5.6 μm so that the density of the concave portions is32000/mm², the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1A.

Comparative Example 2A

Except for setting the depth of the concave portion of the transfer bodymaster to 3.3 μm, the inner diameter of the concave portion to 3.6 μm,setting the distance between centers of the adjacent concave portion to4.2 μm, so that the density of the concave portions is 57000/mm², andusing electrically conductive particles (AUL703, Sekisui Chemical Co.,Ltd.) having an average particle diameter of 3 μm instead ofelectrically conductive particles having an average particle diameter of4 μm, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1A.

Evaluation

“Omission” and “Aggregation” of Electrically Conductive Particles

For the anisotropic electrically conductive films of Examples 1A to 4Aand Comparative Examples 1A to 2A, a region of 1 cm² was observed byusing an optical microscope (MX50, Olympus Corporation) from thetransparent electrically insulating adhesive cover layer side. Then, aproportion of the lattice points at which the electrically conductiveparticle is not deposited within an assumed planar lattice pattern, withrespect to all the lattice points (omission [%]), and a proportion ofthe lattice points at which two or more electrically conductiveparticles were aggregated, with respect to all the lattice points, wereexamined. The obtained results are shown in Table 1.

Also, a longest distance (aggregation distance) between the aggregatedelectrically conductive particles was measured and shown along therewithin Table 1. Note that directions of the “aggregation” were in ahorizontal direction of the anisotropic electrically conductive film forall cases.

Particle Area Occupancy

The particle area occupancy was calculated, from the average particlediameter of the electrically conductive particles and the concaveportion density of the transfer body master (=the convex portion densityof the transfer body), upon considering “omission” and “aggregation” ofthe electrically conductive particles. The obtained results are shown inTable 1.

Initial Conduction Resistance

The anisotropic electrically conductive films in Examples andComparative Examples were used to make an anisotropic conductiveconnection between an IC chip that had a gold bump with a height of 15μm and 30×50 μm with a space between bumps of 12 μm and a glasssubstrate on which a wiring of a space of 12 μm was provided underconditions of 180° C. and 60 MPa for five seconds, and the connectionstructural body was obtained. For the obtained connection structuralbody, an initial conduction resistance value was measured by using aresistance measuring instrument (digital multimeter 7565, YokogawaElectric Corporation). The obtained results are shown in Table 1. Theresistance of 0.5Ω or less is desirable.

Conduction Reliability

The connection structural body used in measurement of the initialconduction resistance value was placed in an aging tester set to atemperature of 85° C. and a humidity of 85%, and the electricallyconductive resistance value after being left for 500 hours was measuredin the same manner as the initial conduction resistance. The obtainedresults are shown in Table 1. The results of 5Ω or less is desirable.

Occurrence Rate of Short Circuit

The same connection structural body as that used to measure the initialconduction resistance value was prepared, and the presence or absence ofoccurrence of a short circuit between the adjacent wires wasinvestigated. The obtained results are shown in Table 1. An occurrencerate of short circuit of not greater than 50 ppm is desirable.

TABLE 1 Comparative Example Example 1A 2A 3A 4A 1A 2A Concave portiondensity of [number/mm²] 16000 16000 28000 28000 32000 57000 transferbody master Average particle diameter [μm] 4 4 3 3 4 3 of electricallyconductive particles “Omission” of electrically [%] 15 10 15 18 0.8 0.8conductive particles “Aggregation” of [%] 0.1 5 0.1 5 27 27 electricallyconductive particles Aggregation distance [μm] 0.25 0.1 0.2 0.45 0.2 0.4Particle area occupancy [%] 17.1 19.1 16.8 17.2 50.7 50.8 Initialconduction [Ω] 0.2 0.2 0.2 0.2 0.2 0.2 resistance Conduction reliability[Ω] 4 4 4 4 4 4 Occurrence rate of short [ppm] <50 <50 <50 <50 200 150circuit

From the results in Table 1, it is understood that with respect to eachof the evaluation items of initial conduction resistance, conductionreliability, and occurrence rate of short circuit, the connectionstructural bodies in which the anisotropic electrically conductive filmsof Examples 1A to 4A were used indicated a satisfactory result.

On the other hand, in a case of the anisotropic electrically conductivefilm of Comparative Examples 1A and 2A, a proportion of “aggregation” ofthe electrically conductive particles was too large although aproportion of “omission” thereof was small. Thus, the occurrence rate ofshort circuit was evaluated as poor.

Example 5A

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 500/mm², the transfer body was prepared in the samemanner as Example 2A, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as those inExample 2A, and furthermore, the particle area occupancy was calculated.As a result, the “omission” and the “aggregation” of the electricallyconductive particles were the same as in Example 2A. The particle areaoccupancy was 0.6%.

In addition, the obtained anisotropic electrically conductive film wasinterposed between a glass substrate (ITO solid electrode) and aflexible wiring board (bump width: 200 μm, L (line)/S (space[spacing])=1, wiring height of 10 μm), the anisotropic conductionconnection was made under the conditions of 180° C. and 80 MPa for fiveseconds such that a connection bump length was 1 mm, and the connectionstructural body for evaluation was obtained. Concerning the “initialconduction resistance value” and the “conduction reliability” afterbeing input for 500 hours in a thermostatic bath with a temperature of85° C. and a humidity of 85% RH in the obtained connection structure,conduction resistance was measured using a four terminal method at acurrent of 1 A using a digital multimeter (34401 A, manufactured byAgilent Technologies, Inc.), the “initial conduction resistance value”was evaluated as good in a case where a measurement value was 2Ω or lessand failure in a case where the measurement value exceeds 2Ω, and the“conduction reliability” was evaluated as good in a case where ameasurement value was 5Ω or less and failure in a case where themeasurement value was 5 (or greater. As a result, every connectionstructural body of Example 5A was evaluated as “good”. When the“occurrence rate of a short circuit” was measured in the same way as inExample 2A, a similar good result was obtained as in Example 2A.

Example 6A

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 2000/mm², the transfer body was prepared in the samemanner as Example 2A, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as those inExample 2A, and furthermore, the particle area occupancy was calculated.As a result, the “omission” and the “aggregation” of the electricallyconductive particles were the same as in Example 2A. The particle areaoccupancy was 2.4%.

In addition, the connection structural body for evaluation was obtainedby forming anisotropic conductive connection by interposing the obtainedanisotropic electrically conductive film between the glass substrate andthe flexible wiring board in the same manner as in Example 5A. When theobtained connection structural body was evaluated for the “initialconduction resistance”, the “conduction reliability”, and the“occurrence rate of short circuit” in the same manner as in Example 5A,satisfactory results were obtained for all of these.

In the anisotropic electrically conductive film of the first mode of thepresent invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as a referenceregion is set to less than 20%, and moreover, a proportion of “latticepoints at which plural electrically conductive particles are disposed inan aggregated state” with respect to all the lattice points of theplanar lattice pattern is 15% or less. Therefore, in a case where theanisotropic electrically conductive film of the first mode of thepresent invention is applied to anisotropic conductive connection, it ispossible to achieve a good initial conductivity and a good conductionreliability after aging, and it is also possible to suppress occurrenceof a short circuit, therefore it is useful to form anisotropicconductive connection of an IC chip and a wiring board with narrowpitches.

Next, the anisotropic electrically conductive film of the second mode ofthe present invention will be specifically described.

Example 1B

A nickel plate having a thickness of 2 mm was prepared, a cylindricalshaped concave portion (an inner diameter 6 μm and a depth 8 μm) wasformed in a tetragonal lattice pattern. Thus, the transfer body masterwas obtained. The distance between the centers of adjacent concaveportions was 8 μm. Accordingly, the density of concave portions was16000/mm².

The resultant transfer body master was coated with a photopolymerizableresin composition containing 60 parts by mass of phenoxy resin (YP-50,Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylateresin (M208, Toagosei Co., Ltd.), and 2 parts by mass ofphotopolymerization initiator (IRGACURE184, BASF Japan Ltd.) on a PET(polyethylene terephthalate) film to a dried thickness of 30 μm, andafter drying for five minutes at 80° C., light irradiation at 1000 mJwas performed by a high pressure mercury lamp. Thus, the transfer bodywas created.

The transfer body was peeled off from the master, and wound on astainless steel roll with a diameter of 20 cm so that the convexportions were on the outer side. Then, the roll was brought into contactwith an adhesive sheet obtained by impregnating a nonwoven fabric with aweak adhesive composition containing 70 parts by mass of epoxy resin(jER828, Mitsubishi Chemical Corporation) and 30 parts by mass ofphenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) whilerotating the roll. Next, the weak adhesive composition was deposited onthe top surface of the convex portions to form the weak adhesive layerwith a thickness of 1 μm. Thus, the transfer body was obtained.

The electrically conductive particles with an average particle diameterof 4 μm (nickel plated resin particles (AUL704, Sekisui Chemical Co.,Ltd.)) were scattered on the surface of the transfer body, andsubsequently, the electrically conductive particles, which were notdeposited to the weak adhesive layer, were removed by blowing.

The transfer body, to which the electrically conductive particles weredeposited, was pressed, at a temperature of 50° C. and with a pressureof 0.5 MPa, from the side on which electrically conductive particleswere deposited, against a sheet-shaped thermosetting-type electricallyinsulating adhesive film with a thickness of 5 μm that is theelectrically insulating adhesive base layer (a film formed from anelectrically insulating adhesive composition containing 60 parts by massof phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 40parts by mass of epoxy resin (jER828, Mitsubishi Chemical Corporation),2 parts by mass of cationic curing agent (SI-60L, Sanshin ChemicalIndustry Co., Ltd.), and 20 parts by mass of silica fine particles(Aerosil RY200, Nippon Aerosil Co., Ltd.)). Thus, the electricallyconductive particles were transferred to the electrically insulatingadhesive base layer.

On the side of the electrically insulating adhesive base layer obtained,on which the electrically conductive particles were deposited, anothersheet-shaped electrically insulating adhesive film with a thickness of15 μm (film formed from an insulating adhesive composition containing 60parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin ChemicalCo., Ltd.), 40 parts by mass of epoxy resin (jER828, Mitsubishi ChemicalCorporation), and 2 parts by mass of cationic curing agent (SI-60L,Sanshin Chemical Industry Co., Ltd.)) was overlapped as a transparentelectrically insulating adhesive cover layer and laminated together at atemperature of 60° C. and with a pressure of 2 MPa. Thereby, theanisotropic electrically conductive film was obtained.

Example 2B

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 1B, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1B.

Example 3B

Except for setting the inner diameter and the depth of the cylindricalconcave portions of the transfer body master to 4.5 μm and 7.5 μm,respectively, setting the distance between the centers of adjacentconcave portions to 6 μm, so that the density of the concave portions is28000/mm², and using electrically conductive particles (AUL703, SekisuiChemical Co., Ltd.) having an average particle diameter of 3 μm insteadof electrically conductive particles having an average particle diameterof 4 μm, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1B.

Example 4B

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 3B, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 3B.

Comparative Example 1B

Except for setting the depth of the concave portion of the transfer bodymaster to 4.4 μm, the inner diameter of the concave portions to 4.8 μm,setting the distance between the centers of adjacent concave portions to5.6 μm, so that the density of the concave portions is 32000/mm², theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1B.

Comparative Example 2B

Except for setting the depth of the concave portion of the transfer bodymaster to 3.3 μm, the inner diameter of the concave portions to 3.3 μm,setting the distance between the centers of adjacent concave portions to4.2 μm, so that the density of the concave portions is 57000/mm², andusing electrically conductive particles (AUL703, Sekisui Chemical Co.,Ltd.) having an average particle diameter of 3 μm instead ofelectrically conductive particles having an average particle diameter of4 μm, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1B.

Evaluation

For the anisotropic electrically conductive films of Examples 1B to 4Band Comparative Examples 1B to 2B, the same evaluation items as thoseevaluated for the anisotropic electrically conductive film of Example 1Awere tested and evaluated by the same method. The obtained results areshown in Table 2. Note that direction of the “aggregation” of theaggregated electrically conductive particles was in a horizontaldirection of the anisotropic electrically conductive film for all thecases.

TABLE 2 Comparative Example Example 1B 2B 3B 4B 1B 2B Concave portiondensity of [number/mm²] 16000 16000 28000 28000 32000 57000 transferbody master Average particle diameter [μm] 4 4 3 3 4 3 of electricallyconductive particles “Omission” of electrically [%] 1 4 1 4 0.5 0.5conductive particles “Aggregation” of [%] 14 11 14 11 26 26 electricallyconductive particles Aggregation distance [μm] 0.2 1 0.15 0.75 0.1 0.08Particle area occupancy [%] 22.7 21.5 22.4 21.2 50.4 50.5 Initialconduction [Ω] 0.2 0.2 0.2 0.2 0.2 0.2 resistance Conduction reliability[Ω] 4 4 4 4 4 4 Occurrence rate of short [ppm] <50 <50 <50 <50 400 250circuit

From the results in Table 2, it is understood that the connectionstructural bodies in which the anisotropic electrically conductive filmsin Examples 1B to 4B were used exhibited good results for eachevaluation item of initial conduction resistance, conductionreliability, and occurrence rate of short circuit.

On the other hand, in a case of the anisotropic electrically conductivefilms in Comparative Examples 1B and 2B, a proportion of “aggregation”of the electrically conductive particles was too large although aproportion of “omission” was low, thus the occurrence rate of shortcircuit significantly exceeded 50 ppm.

Example 5B

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 500/mm², the transfer body was prepared in the samemanner as in Example 2B, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as in Example 2B,and furthermore, the particle area occupancy was calculated. As aresult, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2B. The particlearea occupancy was 0.7%.

In addition, the obtained anisotropic electrically conductive film wasinterposed between a glass substrate (ITO solid electrode) and aflexible wiring board (bump width: 200 μm, L (line)/S (space[spacing])=1, wiring height of 10 μm), the anisotropic conductiveconnection was made under the conditions of 180° C. and 80 MPa for fiveseconds such that a connection bump length was 1 mm, and the connectionstructural body for evaluation was obtained. In the obtained connectionstructural body, for the “initial conduction resistance value” and the“conduction reliability” after being placed for 500 hours in athermostatic bath with a temperature of 85° C. and a humidity of 85% RH,conduction resistance was measured using a four terminal method at acurrent of 1 A using a digital multimeter (34401A, manufactured byAgilent Technologies, Inc.), the “initial conduction resistance value”was evaluated as good in a case where a measurement value was 2Ω or lessand failure in a case where the measurement value exceeds 2Ω, and the“conduction reliability” was evaluated as good in a case where ameasurement value was 5Ω or less and failure in a case where themeasurement value was 5 Ω or greater. As a result, the connectionstructural body of Example 5B was evaluated as “good” for all items.When the “occurrence rate of a short circuit” was measured in the samemanner as in Example 2B, a good result was obtained similar to that ofExample 2B.

Example 6B

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 2000/mm², the transfer body was prepared in the samemanner as in Example 2B, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as in Example 2B,and furthermore, the particle area occupancy was calculated. As aresult, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2B. The particlearea occupancy was 2.7%.

In addition, the connection structural body for evaluation was obtainedby forming anisotropic conductive connection by interposing the obtainedanisotropic electrically conductive film between the glass substrate andthe flexible wiring board in the same manner as in Example 5B. When theobtained connection structural body was evaluated for the “initialconduction resistance value”, the “conduction reliability”, and the“occurrence rate of short circuit” in the same manner as in Example 5B,satisfactory results were obtained for all of these.

In the anisotropic electrically conductive film of the second mode ofthe present invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as any referenceregion is set to less than 5%, and moreover, a proportion of “latticepoints at which plural electrically conductive particles are disposed inan aggregated state” with respect to all the lattice points of theplanar lattice pattern is greater than 10% and less than 15%. Therefore,in a case where the anisotropic electrically conductive film of thesecond mode of the present invention is applied to anisotropicconductive connection, it is possible to achieve a good initialconductivity and a good conduction reliability after aging, and it isalso possible to suppress occurrence of a short circuit, therefore it isuseful to form anisotropic conductive connection of an IC chip and awiring board with narrow pitches.

Next, the anisotropic electrically conductive film of the third mode ofthe present invention will be specifically described.

Example 1C

A nickel plate having a thickness of 2 mm was prepared, a cylindricalshaped concave portion (an inner diameter 6 μm and a depth 7 μm) wasformed in a tetragonal lattice pattern. Thus, the transfer body masterwas obtained. The distance between the centers of adjacent concaveportions was 8 μm. Accordingly, the density of concave portions was16000/mm².

The resultant transfer body master was applied with a photopolymerizableresin composition containing 60 parts by mass of phenoxy resin (YP-50,Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylateresin (M208, Toagosei Co., Ltd.), and 2 parts by mass ofphotopolymerization initiator (IRGACURE184, BASF Japan Ltd.) on a PET(polyethylene terephthalate) film to a dried thickness of 30 μm, andafter drying for five minutes at 80° C., light irradiation at 1000 mJwas performed by a high pressure mercury lamp. Thus, the transfer bodywas created.

The transfer body was peeled off from the master, and wound on astainless steel roll with a diameter of 20 cm so that the convexportions were on the outer side. Then, the roll was brought into contactwith an adhesive sheet obtained by impregnating a nonwoven fabric with aweak adhesive composition containing 70 parts by mass of epoxy resin(jER828, Mitsubishi Chemical Corporation) and 30 parts by mass ofphenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) whilerotating the roll. Next, the weak adhesive composition was deposited onthe top surface of the convex portions to form the weak adhesive layerwith a thickness of 1 μm. Thus, the transfer body was obtained.

The electrically conductive particles with an average particle diameterof 4 μm (nickel plated resin particles (AUL704, Sekisui Chemical Co.,Ltd.)) were scattered on the surface of the transfer body, andsubsequently, the electrically conductive particles, which were notdeposited to the weak adhesive layer, were removed by blowing.

The transfer body, to which the electrically conductive particles weredeposited, was pressed, at a temperature of 50° C. and with a pressureof 0.5 MPa, from the side on which electrically conductive particleswere deposited, against a sheet-shaped thermosetting-type electricallyinsulating adhesive film with a thickness of 5 μm that is theelectrically insulating adhesive base layer (a film formed from anelectrically insulating adhesive composition containing 60 parts by massof phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 40parts by mass of epoxy resin (jER828, Mitsubishi Chemical Corporation),2 parts by mass of cationic curing agent (SI-60L, Sanshin ChemicalIndustry Co., Ltd.), and 20 parts by mass of silica fine particles(Aerosil RY200, Nippon Aerosil Co., Ltd.)). Thus, the electricallyconductive particles were transferred to the electrically insulatingadhesive base layer.

On the side of the electrically insulating adhesive base layer obtained,on which the electrically conductive particles were deposited, anothersheet-shaped electrically insulating adhesive film with a thickness of15 μm (film formed from an insulating adhesive composition containing 60parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin ChemicalCo., Ltd.), 40 parts by mass of epoxy resin (jER828, Mitsubishi ChemicalCorporation), and 2 parts by mass of cationic curing agent (SI-60L,Sanshin Chemical Industry Co., Ltd.)) was overlapped as a transparentelectrically insulating adhesive cover layer and laminated together at atemperature of 60° C. and with a pressure of 2 MPa. Thereby, theanisotropic electrically conductive film was obtained.

Example 2C

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample IC, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1C.

Example 3C

Except for setting the inner diameter of the cylindrical concaveportions of the transfer body master to 4.5 μm, setting the distancebetween the centers of adjacent concave portions to 6 μm, so that thedensity of the concave portions is 28000/mm², and using electricallyconductive particles (AUL703, Sekisui Chemical Co., Ltd.) having anaverage particle diameter of 3 μm instead of electrically conductiveparticles having an average particle diameter of 4 μm, the anisotropicelectrically conductive film was obtained by repeating the steps ofExample 1C.

Example 4C

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 3C, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 3C.

Comparative Example 1C

Except for setting the depth of the concave portion of the transfer bodymaster to 4.4 μm, the inner diameter of the concave portions to 4.8 μm,the distance between the centers of adjacent concave portions to 5.6 μm,so that the density of the concave portions is 32000/mm², theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1C.

Comparative Example 2C

Except for setting the depth of the concave portion of the transfer bodymaster to 3.3 μm, the inner diameter of the concave portions to 3.6 μm,the distance between the centers of adjacent concave portions to 4.2 μm,so that the density of the concave portions is 57000/mm², and usingelectrically conductive particles (AUL703, Sekisui Chemical Co., Ltd.)having an average particle diameter of 3 μm instead of electricallyconductive particles having an average particle diameter of 4 μm, theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1C.

Evaluation

For the anisotropic electrically conductive films of Examples 1C to 4Cand Comparative Examples 1C to 2C, the same evaluation items as thoseevaluated for the anisotropic electrically conductive film of Example 1Awere tested and evaluated by the same method. The obtained results areshown in Table 3. Note that direction of the “aggregation” of theaggregated electrically conductive particles was in a horizontaldirection of the anisotropic electrically conductive film for all thecases.

TABLE 3 Comparative Example Example 1C 2C 3C 4C 1C 2C Concave portiondensity of [number/mm²] 16000 16000 28000 28000 32000 57000 transferbody master Average particle diameter [μm] 4 4 3 3 4 3 of electricallyconductive particles “Omission” of electrically [%] 6 10 6 10 0.5 0.5conductive particles “Aggregation” of [%] 9 5 9 5 26 26 electricallyconductive particles Aggregation distance [μm] <0.25 <0.1 <0.2 <0.45<0.2 <0.4 Particle area occupancy [%] 20.7 19.1 20.4 18.8 50.4 50.5Initial conduction [Ω] 0.2 0.2 0.2 0.2 0.2 0.2 resistance Conductionreliability [Ω] 4 4 4 4 4 4 Occurrence rate of short [ppm] <50 <50 <50<50 400 250 circuit

From the results in Table 3, it is understood that the connectionstructural bodies in which the anisotropic electrically conductive filmsin Examples 1C to 4C were used exhibited a good result for eachevaluation item of initial conduction resistance, conductionreliability, and occurrence rate of short circuit.

On the other hand, in a case of the anisotropic electrically conductivefilms of Comparative Examples 1C and 2C, a proportion of “aggregation”of the electrically conductive particles was too large although aproportion of “omission” thereof was low, and thus, the occurrence rateof short circuit was evaluated as poor.

Example 5C

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 500/mm², the transfer body was prepared in the samemanner as in Example 2C, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as in Example 2C,and furthermore, the particle area occupancy was calculated. As aresult, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2C. The particlearea occupancy was 0.6%.

In addition, the obtained anisotropic electrically conductive film wasinterposed between a glass substrate (ITO solid electrode) and aflexible wiring board (bump width: 200 μm, L (line)/S (space[spacing])=1, wiring height of 10 μm), the anisotropic conductiveconnection was made under the conditions of 180° C. and 80 MPa for fiveseconds such that a connection bump length was 1 mm, and the connectionstructural body for evaluation was obtained. In the obtained connectionstructural body, for the “initial conduction resistance value” and the“conduction reliability” after being placed for 500 hours in athermostatic bath with a temperature of 85° C. and a humidity of 85% RH,conduction resistance was measured using a four terminal method at acurrent of 1 A using a digital multimeter (34401A, manufactured byAgilent Technologies, Inc.), the “initial conduction resistance value”was evaluated as good in a case where a measurement value was 2Ω or lessand failure in a case where the measurement value exceeds 2Ω, and the“conduction reliability” was evaluated as good in a case where ameasurement value was 5Ω or less and failure in a case where themeasurement value was 5Ω or greater. As a result, the connectionstructural body of Example 5C was evaluated as “good” for all items.When the “occurrence rate of a short circuit” was measured in the samemanner as in Example 2C, a good result was obtained similar to that ofExample 2C.

Example 6C

Except for adjusting the distance between the centers of adjacentconcave portions in order to use the transfer body master in which theconcave portion density was 2000/mm², the transfer body was prepared inthe same manner as in Example 2C, and furthermore, the anisotropicelectrically conductive film was prepared. For the obtained anisotropicelectrically conductive film, “omission” and “aggregation” of theelectrically conductive particles were measured in the same manner as inExample 2C, and furthermore, the particle area occupancy was calculated.As a result, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2C. The particlearea occupancy was 2.4%.

In addition, the connection structural body for evaluation was obtainedby forming anisotropic conductive connection by interposing the obtainedanisotropic electrically conductive film between the glass substrate andthe flexible wiring board in the same manner as in Example 5C. When theobtained connection structural body was evaluated for the “initialconduction resistance value”, the “conduction reliability”, and the“occurrence rate of short circuit” in the same manner as in Example 5C,satisfactory results were obtained for all of these.

In the anisotropic electrically conductive film of the third mode of thepresent invention, a proportion of “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as a referenceregion is set to 15% or less, and a proportion of “lattice points atwhich plural electrically conductive particles are disposed in anaggregated state” with respect to all the lattice points of the planarlattice pattern is 10% or less. The electrically conductive particlesthat are disposed in the aggregated state are aggregated in contact witheach other in the planar direction of the anisotropic electricallyconductive film. Therefore, in a case where the anisotropic electricallyconductive film of the third mode of the present invention is applied toanisotropic conductive connection, it is possible to achieve a goodinitial conductivity and a good conduction reliability after aging, andit is also possible to suppress occurrence of a short circuit, thereforeit is useful to form anisotropic conductive connection of an IC chip anda wiring board with narrow pitches.

Next, the anisotropic electrically conductive film of the fourth mode ofthe present invention will be specifically described.

Example 1D

A nickel plate having a thickness of 2 mm was prepared, a cylindricalshaped concave portion (an inner diameter 5 μm and a depth 8 μm) wasformed in a tetragonal lattice pattern. Thus, the transfer body masterwas obtained. The distance between the centers of adjacent concaveportions was 8 Jim. Accordingly, the density of concave portions was16000/mm².

The resultant transfer body master was coated with a photopolymerizableresin composition containing 60 parts by mass of phenoxy resin (YP-50,Nippon Steel & Sumikin Chemical Co., Ltd.), 29 parts by mass of acrylateresin (M208, Toagosei Co., Ltd.), and 2 parts by mass ofphotopolymerization initiator (IRGACURE184, BASF Japan Ltd.) on a PET(polyethylene terephthalate) film to a dried thickness of 30 μm, andafter drying for five minutes at 80° C., light irradiation at 1000 mJwas performed by a high pressure mercury lamp. Thus, the transfer bodywas created.

The transfer body was peeled off from the master, and wound on astainless steel roll with a diameter of 20 cm so that the convexportions were on the outer side. Then, the roll was brought into contactwith an adhesive sheet obtained by impregnating a nonwoven fabric with aweak adhesive composition containing 70 parts by mass of epoxy resin(jER828, Mitsubishi Chemical Corporation) and 30 parts by mass ofphenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.) whilerotating the roll. Next, the weak adhesive composition was deposited onthe top surface of the convex portions to form the weak adhesive layerwith a thickness of 1 μm. Thus, the transfer body was obtained.

The electrically conductive particles with an average particle diameterof 4 μm (nickel plated resin particles (AUL704, Sekisui Chemical Co.,Ltd.)) were scattered on the surface of the transfer body, andsubsequently, the electrically conductive particles, which were notdeposited to the weak adhesive layer, were removed by blowing.

The transfer body, to which the electrically conductive particles weredeposited, was pressed, at a temperature of 50° C. and with a pressureof 0.5 MPa, from the side on which electrically conductive particleswere deposited, against a sheet-shaped thermosetting-type electricallyinsulating adhesive film with a thickness of 5 m that is theelectrically insulating adhesive base layer (a film formed from anelectrically insulating adhesive composition containing 60 parts by massof phenoxy resin (YP-50, Nippon Steel & Sumikin Chemical Co., Ltd.), 40parts by mass of epoxy resin (jER828, Mitsubishi Chemical Corporation),2 parts by mass of cationic curing agent (SI-60L, Sanshin ChemicalIndustry Co., Ltd.), and 20 parts by mass of silica fine particles(Aerosil RY200, Nippon Aerosil Co., Ltd.)). Thus, the electricallyconductive particles were transferred to the electrically insulatingadhesive base layer.

On the side of the electrically insulating adhesive base layer obtained,on which the electrically conductive particles were deposited, anothersheet-shaped electrically insulating adhesive film with a thickness of15 m (film formed from an insulating adhesive composition containing 60parts by mass of phenoxy resin (YP-50, Nippon Steel & Sumikin ChemicalCo., Ltd.), 40 parts by mass of epoxy resin (jER828, Mitsubishi ChemicalCorporation), and 2 parts by mass of cationic curing agent (SI-60L,Sanshin Chemical Industry Co., Ltd.)) was overlapped as a transparentelectrically insulating adhesive cover layer and laminated together at atemperature of 60° C. and with a pressure of 2 MPa. Thereby, theanisotropic electrically conductive film was obtained.

Example 2D

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 1D, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 1D.

Example 3D

Except for setting the inner diameter of the cylindrical concaveportions of the transfer body master to 3.8 μm, a depth to 6 μm, settingthe distance between the centers of adjacent concave portions to 6 μm,so that the density of the concave portions is 28000/mm², and usingelectrically conductive particles (AUL703, Sekisui Chemical Co., Ltd.))having an average particle diameter of 3 μm instead of electricallyconductive particles having an average particle diameter of 4 μm, theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1D.

Example 4D

Except for doubling each of the amount of scattered electricallyconductive particles and the number of times of blowing, as compared toExample 3D, the anisotropic electrically conductive film was obtained byrepeating the steps of Example 3D.

Comparative Example 1D

Except for setting the depth of the concave portion of the transfer bodymaster to 4.4 μm, the inner diameter of the concave portions to 4.8 μm,the distance between the centers of adjacent concave portions to 5.6 μm,so that the density of the concave portions is 32000/mm², theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1D.

Comparative Example 2D

Except for setting the depth of the concave portion of the transfer bodymaster to 3.3 μm, the inner diameter of the concave portions to 3.6 μm,the distance between the centers of adjacent concave portions to 4.2 μm,so that the density of the concave portions is 57000/mm², and usingelectrically conductive particles (AUL703, Sekisui Chemical Co., Ltd.)having an average particle diameter of 3 μm instead of electricallyconductive particles having an average particle diameter of 4 μm, theanisotropic electrically conductive film was obtained by repeating thesteps of Example 1D.

Evaluation

For the anisotropic electrically conductive films of Examples 1D to 4Dand Comparative Examples 1D to 2D, the same evaluation items as thoseevaluated for the anisotropic electrically conductive film of Example 1Awere tested and evaluated by the same method. The obtained results areshown in Table 4. Note that direction of the “aggregation” of theaggregated electrically conductive particles was in a horizontaldirection of the anisotropic electrically conductive film for all thecases.

TABLE 4 Comparative Example Example 1D 2D 3D 4D 1D 2D Concave PortionDensity of [number/mm²] 16000 16000 28000 28000 32000 57000 TransferBody Master Average particle diameter [μm] 4 4 3 3 4 3 of electricallyconductive particles “Omission” of electrically [%] 6 4 6 4 1 1conductive particles “Aggregation” of [%] 9 11 9 11 26 26 electricallyconductive particles Aggregation distance [μm] 2 1.1 1.5 0.76 0.8 0.6Particle area occupancy [%] 20.7 21.5 20.4 21.2 50.2 50.3 Initialconduction [Ω] 0.2 0.2 0.2 0.2 0.2 0.2 resistance Conduction reliability[Ω] 4 4 4 4 4 4 Occurrence rate of short [ppm] <50 <50 <50 <50 150 100circuit

From the results in Table 4, it is understood that the connectionstructural bodies in which the anisotropic electrically conductive filmsin Examples 1D to 4D were used exhibited a good result for eachevaluation item of initial conduction resistance, conductionreliability, and occurrence rate of short circuit.

On the other hand, in a case of the anisotropic electrically conductivefilms of Comparative Examples 1D and 2D, a proportion of “aggregation”of the electrically conductive particles was too large although aproportion of “omission” is low, and thus, the occurrence of a shortcircuit was evaluated as poor.

Example 5D

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 500/mm², the transfer body was prepared in the samemanner as in Example 2D, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as in Example 2D,and furthermore, the particle area occupancy was calculated. As aresult, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2D. The particlearea occupancy was 0.7%.

In addition, the obtained anisotropic electrically conductive film wasinterposed between a glass substrate (ITO solid electrode) and aflexible wiring board (bump width: 200 μm, L (line)/S (space[spacing])=1, wiring height of 10 μm), the anisotropic conductiveconnection was made under the conditions of 180° C. and 80 MPa for fiveseconds such that a connection bump length was 1 mm, and the connectionstructural body for evaluation was obtained. In the obtained connectionstructural body, for the “initial conduction resistance value” and the“conduction reliability” after being placed for 500 hours in athermostatic bath with a temperature of 85° C. and a humidity of 85% RH,conduction resistance was measured using a four terminal method at acurrent of 1 A using a digital multimeter (34401A, manufactured byAgilent Technologies, Inc.), the “initial conduction resistance value”was evaluated as good in a case where a measurement value was 2Ω or lessand failure in a case where the measurement value exceeds 2Ω, and the“conduction reliability” was evaluated as good in a case where ameasurement value was 5Ω or less and failure in a case where themeasurement value was 5Ω or greater. As a result, every connectionstructural body of Example 5D was evaluated as “good” for all items.When the “occurrence rate of a short circuit” was measured in the samemanner as in Example 2D, a good result was obtained similar to that ofExample 2D.

Example 6D

Except for adjusting the distance between the centers of adjacentconcave portions to use the transfer body master in which the concaveportion density was 2000/mm², the transfer body was prepared in the samemanner as in Example 2D, and furthermore, the anisotropic electricallyconductive film was prepared. For the obtained anisotropic electricallyconductive film, “omission” and “aggregation” of the electricallyconductive particles were measured in the same manner as in Example 2D,and furthermore, the particle area occupancy was calculated. As aresult, the “omission” and the “aggregation” of the electricallyconductive particles were the same as those in Example 2D. The particlearea occupancy was 2.7%.

In addition, the connection structure for evaluation was obtained bymaking anisotropic conductive connection with interposing the obtainedanisotropic electrically conductive film between the glass substrate andthe flexible wiring board in the same manner as Example 5D. When theobtained connection structural body was evaluated for the “initialconduction resistance value”, the “conduction reliability”, and the“occurrence rate of short circuit” in the same manner as in Example 5D,satisfactory results were obtained for all of these.

In the anisotropic electrically conductive film of the fourth mode ofthe present invention, a proportion of the “lattice points, at which noelectrically conductive particle is disposed” with respect to all thelattice points of the planar lattice pattern assumed as the referenceregion is set to less than 10%, and a proportion of “lattice points atwhich plural electrically conductive particles are disposed in anaggregated state” with respect to all the lattice points of the planarlattice pattern is set to 15% or less, and moreover, at least some ofthe electrically conductive particles disposed in an aggregated stateare disposed with an oblique shift in a thickness direction of theanisotropic electrically conductive film. Therefore, in a case where theanisotropic electrically conductive film of the fourth mode of thepresent invention is applied to anisotropic conductive connection, it ispossible to achieve a good initial conductivity and a good conductionreliability after aging, and it is also possible to suppress occurrenceof a short circuit, therefore it is useful to establishing anisotropicconductive connection of an IC chip and a wiring board with narrowpitches.

REFERENCE SIGNS LIST

-   10, 200 Anisotropic electrically conductive film-   11, 104 Electrically insulating adhesive base layer-   12, 105 Electrically insulating adhesive cover layer-   13, 103 Electrically conductive particle-   100 Transfer body-   101 Convex portion-   102 Weak adhesive layer-   A Lattice point at which electrically conductive particle is not    present (position at which electrically conductive particle is not    disposed at a lattice point)-   B Lattice point where electrically conductive particles are    aggregated in contact with each other (position at which    electrically conductive particles are aggregated in contact with    each other)-   C Lattice point at which electrically conductive particles are    aggregated to be spaced apart with one another (position at which    electrically conductive particles are aggregated in non-contact    manner)

The invention claimed is:
 1. An anisotropic electrically conductive film having a structure, in which electrically conductive particles are disposed at lattice points of a planar lattice pattern in an electrically insulating adhesive base layer, wherein: in a planar lattice pattern assumed as a reference region of the anisotropic electrically conductive film, lattice points at which no electrically conductive particle is disposed exist, and a proportion of the lattice points at which no electrically conductive particle is disposed, with respect to all lattice points of the reference region, is less than 20%, and a particle area occupancy with respect to an area of the reference region of the anisotropic electrically conductive film, of all electrically conductive particles present in the area, is not less than 0.15%.
 2. The anisotropic electrically conductive film according to claim 1, wherein the reference region is a substantially square region including a side X and a side Y in a center portion of a plane of the anisotropic electrically conductive film, the side X and the side Y satisfying Relationships (A), (2), and (3): 100D≤X+Y≤400D  (A) X≥5D  (2) Y≥5D  (3) where D is an average particle diameter of the electrically conductive particles, the side Y is a straight line disposed at an angle in a range of less than ±45° with respect to a longitudinal direction of the anisotropic electrically conductive film, and the side X is a straight line perpendicular to the side Y.
 3. The anisotropic electrically conductive film according to claim 1, wherein an insulating adhesive cover layer is further provided on the insulating adhesive base layer.
 4. The anisotropic electrically conductive film according to claim 1, wherein a particle area occupancy with respect to an area of the reference region of the anisotropic electrically conductive film, of all the electrically conductive particles present in the area, is 35% or less.
 5. The anisotropic electrically conductive film according to claim 1, wherein an average particle diameter of the electrically conductive particles is from 1 to 10 μm, and a distance between adjacent lattice points of the planar lattice pattern is greater than 0.5 times the average particle diameter of the electrically conductive particles.
 6. The anisotropic electrically conductive film according to claim 1, wherein when some of the electrically conductive particles are absent, absence of four or more consecutive electrically conductive particles in a longitudinal direction of the anisotropic electrically conductive film and absence of four or more consecutive electrically conductive particles in a direction perpendicular to the longitudinal direction of the anisotropic electrically conductive film do not intersect.
 7. The anisotropic electrically conductive film according to claim 1, wherein when some of the electrically conductive particles are absent, any of an absence of four or more consecutive electrically conductive particles is not adjacent to each other, via one or more electrically conductive particles being lattice points.
 8. The anisotropic electrically conductive film according to claim 1, wherein 11 or more electrically conductive particles are consecutively disposed in a direction perpendicular to a longitudinal direction of the anisotropic electrically conductive film.
 9. The anisotropic electrically conductive film according to claim 1, wherein at least either one of metal particles and metal-coated resin particles are used as the electrically conductive particles.
 10. The anisotropic electrically conductive film according to claim 1, wherein the planar lattice pattern is a rhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, or a parallelotope lattice.
 11. The anisotropic electrically conductive film according to claim 1, wherein an electrically insulating filler is added to the electrically insulating adhesive base layer.
 12. The anisotropic electrically conductive film according to claim 1, wherein an electrically insulating filler is added to the electrically insulating adhesive cover layer.
 13. A connection structural body having a terminal of a first electronic component and a terminal of a second electronic component being anisotropically electrically conductive connected by the anisotropic electrically conductive film described in claim
 1. 14. A method for producing a connection structural body, the method comprising anisotropically electrically conductive connecting a terminal of a first electronic component and a terminal of a second electronic component by the anisotropic electrically conductive film described in claim
 1. 15. The anisotropic electrically conductive film according to claim 2, wherein the reference region is a substantially square region including a side X and a side Y in a center portion of a plane of the anisotropic electrically conductive film, the side X and the side Y satisfying Relationships (1) to (3): X+Y=100D X≥5D Y≥5D
 16. An anisotropic electrically conductive film having a structure, in which electrically conductive particles are disposed at lattice points of a planar lattice pattern in an electrically insulating adhesive base layer, wherein: in a planar lattice pattern assumed as a reference region of the anisotropic electrically conductive film, a proportion of lattice points at which a plurality of electrically conductive particles are disposed in an aggregated state, with respect to all lattice points of the reference region, is not greater than 15%, and a particle area occupancy, with respect to an area of the reference region of the anisotropic electrically conductive film, of all electrically conductive particles present in the area, is not less than 0.15%.
 17. The anisotropic electrically conductive film according to claim 16, wherein the reference region is a substantially square region including a side X and a side Y in a center portion of a plane of the anisotropic electrically conductive film, the side X and the side Y satisfying relationships: X+Y=400D   (1) X≥20D   (2) Y≥20D   (3).
 18. The anisotropic electrically conductive film according to claim 16, wherein an insulating adhesive cover layer is further provided on the insulating adhesive base layer.
 19. The anisotropic electrically conductive film according to claim 16, wherein a particle area occupancy with respect to an area of the reference region of the anisotropic electrically conductive film, of all the electrically conductive particles present in the area, is 35% or less.
 20. The anisotropic electrically conductive film according to claim 16, wherein an average particle diameter of the electrically conductive particles is from 1 to 10 μm, and a distance between adjacent lattice points of the planar lattice pattern is greater than 0.5 times the average particle diameter of the electrically conductive particles.
 21. The anisotropic electrically conductive film according to claim 16, wherein there are not more than three sets of the electrically conductive particles that are connected by two in the vicinity of the electrically conductive particles aggregated by two.
 22. A connection structural body having a terminal of a first electronic component and a terminal of a second electronic component being anisotropically electrically conductive connected by the anisotropic electrically conductive film described in claim
 16. 23. A method for producing a connection structural body, the method comprising anisotropically electrically conductive connecting a terminal of a first electronic component and a terminal of a second electronic component by the anisotropic electrically conductive film described in claim
 16. 24. The anisotropic electrically conductive film according to claim 16, wherein 11 or more electrically conductive particles are consecutively disposed in a direction perpendicular to a longitudinal direction of the anisotropic electrically conductive film.
 25. The anisotropic electrically conductive film according to claim 16, wherein at least either one of metal particles and metal-coated resin particles are used as the electrically conductive particles.
 26. The anisotropic electrically conductive film according to claim 16, wherein the planar lattice pattern is a rhombic lattice, a hexagonal lattice, a square lattice, a rectangular lattice, or a parallelotope lattice.
 27. The anisotropic electrically conductive film according to claim 16, wherein an electrically insulating filler is added to electrically insulating filler is added to the electrically insulating adhesive base layer.
 28. The anisotropic electrically conductive film according to claim 16, wherein an electrically insulating filler is added to the electrically insulating adhesive cover layer. 